Surgical drill having a brake that, upon the drill bit penetrating through bone, prevents further insertion of the drill

ABSTRACT

A surgical drill for use with a drill bit. The drill includes a handpiece with a motor and a brake mechanism. The brake mechanism is a sliding rack adjacent a first end and a second end with a stop adjacent the drill bit. An actuator is mounted to the handpiece and a plunger is coupled to the actuator. A sensor asserts a signal when the drill bit penetrates bone. When the sensor asserts the signal indicting the drill bit penetrated bone, the actuator moves the plunger into engagement with the rack to prevent further insertion of the drill bit.

FIELD OF THE INVENTION

This invention relates generally to surgical drills used to form a borein a bone. More particularly, the surgical drill of the presentinvention has a brake mechanism that upon the drill bit penetratingthrough the bone, prevents further insertion of the drill bit.

BACKGROUND OF THE INVENTION

In modern surgery, one of the most important instruments available tomedical personnel is the powered surgical drill. Typically, this drillcomprises a housing in which a motor is secured called a handpiece. Themotor has a shaft that is connected to some type of chuck or othercoupling assembly that is mounted to the housing. The coupling assemblyholds a cutting accessory that is applied to the patient in order toperform a specific medical procedure. Some common cutting accessoriesare drill bits, burs and reamers. These accessories are used to drillinto and/or separate sections of soft tissue and hard tissue, commonlyreferred to as bone. The ability to use surgical drills to actuate theseand other cutting accessories has lessened the physical strain ofphysicians and other medical personnel that perform these medicalprocedures. Moreover, most surgical procedures can be performed morequickly and more accurately with powered surgical tools than with themanual equivalents that preceded them.

Surgical drills are often used in certain orthopedic surgical proceduresin order to facilitate the repair of fractured and broken bones. Thesefractures and breaks typically occur as a result of trauma to the bone.In this type of procedure it is common practice to fit a pin or screw tothe adjacent sections of the bone so as to hold these sections together.In this type of procedure, the drill is used to form a bore/hole/holesin the section/sections of the bone into which the pin or screw is to befitted.

In this type of procedure, the drill bit, while it should extend throughthe bone, should not be pressed to extend beyond the bone. This isbecause if the tip of the drill bit, presses through the bone, the tipcould damage the soft tissue adjacent the opposite side of the bone.This damage is more likely to occur if the tip, when pressed against thesoft tissue, is rotating.

Accordingly, when a surgeon is forming a bore in a bone in order to seta pin or a screw, the surgeon must typically use extreme care to ensurethat, as soon as possible after the drill bit tip penetrates the bone,the drill is deactivated.

One means suggested to reduce the extent to which a rotating drill bitis allowed to press into soft tissue adjacent a bone is to providetrauma surgeons with drills similar to the cranial perforators used byneurosurgeons. A cranial perforator is a drill used by a neurosurgeon toform the initial entrance opening into the skull. A cranial perforatorincludes a head and inner and outer drills. The inner drill is in theform of a solid cylinder. The outer drill is in the form of a sleevethat extends circumferentially around the inner drill. Both drill bitsextend from the head. The head is attached to handpiece with a motor.Internal to both the head and the drill bits are features that, whenengaged, cause the drill bits to rotate with the rotation of the head.Also, internal to the head is a spring. The spring normally holds atleast one of the drills away from the complementary features integralwith the head. When the drill bits are pressed against bone, theresistance of the bone pushes the drill bit and head features intoengagement. When the perforator is in this state, the rotation of thehead results in a like rotation of the drills. The rotational moment andforward force of the drills causes the drills to form the desired bore.When at least one of the drills, typically the inner drill, completelypenetrates the skull, the skull no longer offers resistance to therelease action of the spring. The spring pushes the drills away from thehead. Thus, when the perforator is in this state, the rotation of thehead does not cause a like rotation of the drills. Since the drills arenot rotating when the perforator is in the this state, the pressing ofthe drills against the tissue, the thin soft tissue below the skull doesnot result in appreciable damage to this tissue.

One reason cranial perforators work well for forming bores in the skullis that the skull is relatively thin. Typically the skull has athickness of 1.5 cm or less. Thus, once the bore is formed, the surgeon,with using only a minimal amount of force, can pull the perforator outof the newly formed bore.

In trauma surgeries and other orthopedic surgeries the surgeon may wantto form a bore hole in bone that is relatively thick, having a thicknessof 3.0 cm or more. Owing to the tight fit of the drill bit in the bore,it is rather difficult to simply pull the bit out of the bone. If amedical practitioner uses a large amount of manual force, there is thepossibility that if they use this back force, especially if coupled witha back and forth prying action, can damage the bone.

To avoid the possibility of this post bore formation bone damage, anorthopedic surgeon typically drives the drill bit in reverse in order tofacilitate the backing out of the bit from the bore. However, asmentioned above, once the drills of a cranial perforator penetrate thebone, they are disengaged from the complementary head. Driving the headin reverse does not foster a like rotational movement of the drills.This is why cranial perforators, while useful for preventing damage tothe tissue underlying the bone against which they are pressed, have notproven particularly suitable for forming the relatively deep boresrequired by orthopedic surgeons.

Another problem with the use of cranial perforators is that during theformation of a bore, the drill bit may disengage from the motor beforethe bore is completely formed. The orthopedic surgeon may need to removethe drill and then re-drill the bore again to complete the formation ofthe bore.

The Inventor's U.S. patent application Ser. No. 13/798,866, filed 13Mar. 2013, now US Pat. Pub. No. US 2013/0245629 A1, the contents ofwhich are hereby incorporated by reference, discloses a perforator likedevice for drilling into bone where a clutch mechanism both preventsoverdrilling and allows the drill bit to be driven in the reversedirection. A limitation of this device is that it requires a bitassembly that includes inner and outer bits. Many orthopedic surgeonsprefer working with a bit assembly that consists of a single drill bit.

An additional issue faced by orthopedic surgeons is that it is difficultand time consuming during surgery to use the current depth gauges todetermine the depth of a bone bore. Current depth gauges use a piece ofwire with a hook to try and measure the depth of the bore. The wire andhook is placed through the bone bore and moved until the hook catches onthe bone adjacent the bottom of the bore. The surgeon places theirfinger on the wire adjacent the bore and removes the wire from the bore.The distance between the surgeon's finger and the hook represents thedepth of the bore.

Unfortunately, if the surgeon's finger is placed incorrectly or slips,the measurement will be incorrect. Also, when the hook extends throughthe bone bore and out from the bottom of the bore, adjacent tissues canbe subject to damage.

SUMMARY OF THE INVENTION

This invention is related to a new and useful surgical drill assemblyused to form a bore in a bone. The surgical drill assembly has a brakemechanism that, upon the drill bit penetrating through the bone,prevents further insertion of the drill bit.

The surgical drill assembly includes a handpiece having a case and arotary motor mounted within the case. A chuck is coupled to the motor.The chuck receives the drill bit. A brake mechanism is coupled to thecase. The brake mechanism includes a rack with a first end and a secondend. The first end of the rack is coupled to the case for slidingmovement relative to the case and the second end has a protector thatsurrounds the drill bit. An actuator is coupled to the case. A plungeris coupled to the actuator and is positioned to be engaged anddisengaged with the rack. A sensor is coupled to the handpiece and isconfigured to sense a first parameter associated with the motor or thedrill bit. A controller is in communication with the motor, the actuatorand the sensor. In response to the first parameter being greater than apre-determined threshold, the controller causes the actuator to move theplunger into engagement with the rack preventing further insertion ofthe drill bit.

The drill assembly of this invention is designed for use with a bitassembly only includes a single piece drill bit.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention is pointed out with particularity in the claims. The aboveand further features and advantages of this invention are understoodfrom the following Detailed Description taken in conjunction with theaccompanying drawings in which:

FIG. 1 is an overall side view of a powered rotary surgical drill havinga top mounted brake mechanism with an external telescoping rack inaccordance with the present invention;

FIG. 2 is a partial exploded view of handpiece components of the rotarysurgical drill of FIG. 1;

FIG. 3 is a side cross-sectional view of the rotary surgical drill ofFIG. 1.

FIG. 3A is a perspective view of the head of the motor rotor depicted inFIG. 3;

FIGS. 3B and 3C are enlarged portions of the cross sectional view ofFIG. 3;

FIG. 4 is an exploded view of the brake mechanism of the rotary surgicaldrill of FIG. 1;

FIG. 5A is an exploded perspective view of the brake mechanism inaccordance with the present invention;

FIG. 5B is an enlarged cross-sectional view of the brake mechanismmounted to the handpiece;

FIG. 6A is a perspective view of the brake mechanism housing;

FIG. 6B is a rear view of the brake mechanism housing;

FIG. 6C is a top view of the brake mechanism housing;

FIG. 6D is a bottom view of the brake mechanism housing;

FIG. 7A is a top perspective view of a solenoid;

FIG. 7B is a bottom perspective view of the solenoid;

FIG. 8A is a perspective view of the brake mechanism plunger;

FIG. 8B is a left side view of the brake mechanism plunger;

FIG. 9A is a top perspective view of the brake mechanism cover;

FIG. 9B is a bottom perspective view of the brake mechanism cover;

FIG. 10A is a top perspective view of the brake mechanism cap;

FIG. 10B is a bottom perspective view of the brake mechanism cap;

FIG. 11 is a top perspective view of a rack and digital caliper;

FIG. 12A is a top perspective view of a drill bit mounted in the tissueprotector in accordance with the present invention;

FIG. 12B is a top perspective view of the tissue protector;

FIG. 13 is a electrical schematic diagram view of the controller andassociated components of the rotary surgical drill of FIG. 1 inaccordance with the present invention;

FIG. 14A is a side cross-sectional view of the tissue protector anddrill bit of FIG. 1 prior to the start of drilling into a bone;

FIG. 14B is a side cross-sectional view of the tissue protector anddrill bit of FIG. 1 during formation of a bone bore in a bone;

FIG. 14C is a side cross-sectional view of the tissue protector anddrill bit of FIG. 1 after the drill bit has penetrated through the bone;

FIG. 15 is a flow chart of a method of operating the rotary surgicaldrill of FIG. 1 in accordance with the present invention;

FIG. 16 is an overall perspective view of another embodiment of apowered rotary surgical drill having an end mounted brake mechanism withan external telescoping rack in accordance with the present invention;

FIG. 17 is a partial front perspective exploded view of components ofthe rotary surgical drill of FIG. 16;

FIG. 18 is a partial rear perspective exploded view of components of therotary surgical drill of FIG. 16;

FIG. 19 is a side cross-sectional view of the rotary surgical drill ofFIG. 16;

FIG. 20 is an enlarged cross-sectional view of the brake mechanism ofFIG. 16;

FIG. 21 is a front perspective view of the brake mechanism housing;

FIG. 22 is a rear perspective view of the brake mechanism housing;

FIG. 23 is a rear view of the brake mechanism housing;

FIG. 24 is a side view of the rack used with the rotary surgical drillof FIG. 16;

FIG. 25 is a perspective view of a depth gauge gear;

FIG. 26 is an overall perspective view of another embodiment of apowered rotary surgical drill having an end mounted brake mechanism withan internal telescoping rack in accordance with the present invention;

FIG. 27 is a front perspective exploded view of components of the rotarysurgical drill of FIG. 26;

FIG. 28 is cross-sectional view of the powered rotary surgical drill ofFIG. 26;

FIG. 29 is an enlarged cross-sectional view of the brake mechanism ofFIG. 26;

FIG. 30 is front perspective view of the outer coupler;

FIG. 31 is a side cross-sectional view of the outer coupler;

FIG. 32 is a front perspective view of the drill bit, tissue protector,rods, plunger, rack and motor shaft showing the relative orientation ofthe components;

FIG. 33 is a front perspective view of the tissue protector, rods andplunger;

FIG. 34 is a front perspective view of the stop;

FIG. 35A is a front perspective view of the tissue protector;

FIG. 35B is a rear perspective view of the tissue protector;

FIG. 36 is a front perspective view of the static tube that extendsthrough the cannulated shaft of the motor;

FIG. 37A is a front perspective view of the rack and coil springs;

FIG. 37B is a side view of the rack;

FIG. 38 is a front perspective view of the spring retainer;

FIG. 39 is a perspective view looking into the brake housing showing therelative orientation of the components when the linear actuator ismounted in the housing;

FIG. 40 is a rear perspective view of the rotary surgical drill of FIG.26 with the brake housing removed showing the relative orientation ofthe linear actuator and the rack;

FIG. 41A is a side cross-sectional view of the tissue protector anddrill bit of FIG. 26 prior to the start of drilling into a bone;

FIG. 41B is a side cross-sectional view of the tissue protector anddrill bit of FIG. 26 during formation of a bone bore in a bone;

FIG. 41C is a side cross-sectional view of the tissue protector anddrill bit of FIG. 26 after the drill bit has penetrated through thebone;

FIG. 42 is an overall perspective view of an additional embodiment of apowered rotary surgical drill having a brake mechanism with a retractingsleeve mechanism in accordance with the present invention;

FIG. 43 is a front perspective view of the brake mechanism of FIG. 26including the chuck assembly and the retracting sleeve mechanism;

FIG. 44A is a right side view of the brake mechanism of FIG. 26 with theretracting sleeve mechanism in a fully extended position;

FIG. 44B is a side cross-sectional view of the brake mechanism of FIG.26 with the retracting sleeve mechanism in a fully extended position;

FIG. 45A is a left side view of the brake mechanism of FIG. 26 with theretracting sleeve mechanism in a fully retracted position;

FIG. 45B is a side cross-sectional view of the brake mechanism of FIG.26 with the retracting sleeve mechanism in a fully retracted position;

FIG. 46 is an exploded view of the brake mechanism of FIG. 43;

FIG. 47 is a exploded rear perspective view of the components of thechuck assembly and the drill bit retainer assembly;

FIG. 48 is a front perspective view of the input drive shaft;

FIG. 49 is a rear perspective view of the inner release collar;

FIG. 50 is a rear perspective view of the plunger and the pin holder;

FIG. 51 is an enlarged cross-sectional view of the chuck assembly andthe drill bit retainer assembly illustrating the relative orientation ofthe components;

FIG. 52 is a front perspective view of the drill bit;

FIG. 53A is a front perspective view of the connecting hub;

FIG. 53B is a side cross-sectional view of the connecting hub;

FIG. 54 is a front perspective view of the release ring;

FIG. 55 is an enlarged side cross-sectional view of the first releasemechanism, the planetary gear assembly and the proximal portion of theretracting sleeve mechanism illustrating the relative orientation of thecomponents;

FIG. 56 is a front perspective view of the ring gear;

FIG. 57A is a front perspective view of the output drive shaft;

FIG. 57B is a front perspective cross-sectional view of the output driveshaft;

FIG. 58 is a front perspective view of the ball nut;

FIG. 59A is a front perspective view of the coupler;

FIG. 59B is a rear perspective view of the coupler;

FIG. 59C is a side cross-sectional view of the coupler;

FIG. 60 is a front perspective view of the tissue protector sleeve;

FIG. 61 is an enlarged side cross-sectional view of the second releasemechanism and the distal portion of the retracting sleeve mechanismillustrating the relative orientation of the components;

FIG. 62A is a side cross-sectional view of the tissue protector sleeveand drill bit of FIG. 42 prior to the start of drilling into a bone;

FIG. 62B is a side cross-sectional view of the tissue protector sleeveand drill bit of FIG. 42 during formation of a bone bore in a bone; and

FIG. 62C is a side cross-sectional view of the tissue protector sleeveand drill bit of FIG. 42 after the drill bit has penetrated through thebone.

DETAILED DESCRIPTION

I. Handpiece

FIGS. 1, 2 and 3 illustrate a rotary surgical drill 100 in accordancewith the present invention. Rotary surgical drill 100 compriseshandpiece 102, chuck assembly 140, drill bit 180, controller 450 andbrake mechanism 200.

Rotary surgical drill 100 includes a handpiece 102. Handpiece 102 has acase or upper housing 103 and a handle 104 that extends downwardly fromthe case or upper housing 103. Handle 104 is generally in the form of apistol grip that can be grasped during use by a medical practitioner.Handle 104 has a lower end 108. The case or upper housing 103 isgenerally cylindrical in shape and has a distal end 106 and a proximalend 107. The case or upper housing 103 has an internal cylindricalshaped cavity 120. The upper housing 103 and handle 104 are formed fromsuitable materials such as metals.

In the discussion of surgical drill 100, “Distal”, it shall beunderstood means away from the practitioner holding the drill 100;towards the surgical site to which the surgical drill 100 is directed.“Proximal”, means towards the practitioner, away from the surgical site.

A rotary electric motor 122 is mounted in cavity 120. In one embodiment,the electric motor 122 is a brushless DC motor. In another embodimentthe motor can be an AC motor, or a pneumatic or hydraulically drivenmotor. Electric motor 122 includes a stator 123 Also part of motor 122are windings 126 that are wound around the stator 123. A rotor 124 isrotatably disposed in stator 123. Rotor 124 is formed so as to have anaxially extending through bore, (bore not identified). Rotor 124 hashead 127, seen in FIG. 3C, that is the form of a gear. In FIG. 3A a tubelike sleeve 125 is shown extending proximally from head 127. When drill100 is assembled, sleeve 127 is press fit in the open distal end of themotor rotor 124 so that the sleeve and head rotate with the rotor. Thisis for manufacturing purposes only. In alternative versions of theinvention, head 127 may be integrally formed with the motor rotor.

A tube 129, seen in FIGS. 3 and 36, extends through and is staticallymounted in motor rotor 124. Tube 129 has a proximal end 131 that islocated proximal to motor rotor 124. The tube has a distal end 132located distal to the motor rotor 124. In the depicted version of theinvention, the distal section of tube 129 that defines the distal end132 has inner and outer diameters that are less than the correspondingdiameters of the proximal end 129. Tube 129 has a lumen 976 with aproximal opening 974 and a distal opening 975. Tube section 977 is thetapered transition section between the large proximal section of thetube and the smaller diameter distal section. When handpiece 102 isassembled sleeve 125 surrounds the distal section of tube 129.

Tube proximal end 131 is disposed in an end cap 133 disposed in theproximal end face of cover 110 as seen in FIG. 3A. Forward of end cap133, tube extends through a static sleeve 135 internal handpiece 102. AnO-ring 137 forms a barrier between the outer surface of tube 129 andsleeve 135. Tube distal end 132 extends through a planetary gearassembly 128 as seen in FIG. 3C. Planetary gear assembly 128 has twocarriers 145 and 147. The distal section of tube 129 extends through theproximal carrier, carrier 145 and terminates in the distal carrier,carrier 147. An O-ring 149 provides a seal between the outer surface oftube 129 and the inner surface of distal carrier 147. Tube 129 is heldstatic in handpiece 102 by the compression fitting of the tube in cap133 and the force exerted by O-ring 137.

Rotor head 127 is the sun gear of planetary gear assembly 128. Moreparticularly rotor head 127 is the sun gear of the planet gearsconnected to carrier 145. Carrier 145 has a sun gear, (not identified).The sun gear of carrier 145 drives the planet gears attached to carrier147. Carrier 147 is connected to chuck assembly 140. Planetary gearassembly 128 drives chuck assembly 140 at a slower rotational rate thanthat of motor 122. A cover 110 is mounted over the proximal end 107 ofhousing 103 enclosing motor 122 within cavity 120. A shroud 111 ismounted over the distal end 106 of housing 103. Shroud 111 has anopening 112 that receives one end of chuck assembly 140.

Handle 104 allows a user to grasp and manipulate the rotary surgicaldrill 100. The handle 104 is hollow and has an internal chamber 105. Aforward trigger switch 116 and a reverse trigger switch 117 extenddistally forward from the front face of handle 104. A printed circuitboard (PCB) 118 is mounted in the chamber 105 internal to handle 104.The PCB 118 is electrically connected to the motor 122 and to thetrigger switches 116 and 117 by one or more wires 119. PCB 118 containsa controller 450 that monitors the actuation of the trigger switches 116and 117. Based on the extent to which the trigger switches 116 and 117are depressed, the controller 450 selectively energizes the motor 122 tocause the motor shaft 130 to rotate at the desired speed. A rechargeablebattery 150 is removably attached to the bottom end of handle 104 and iselectrically connected to PCB 118 and motor 122. Battery 150 suppliespower to rotary surgical drill 100.

Surgical drill 100 further comprises a drill bit 180. A brake mechanism200, also part of drill 100, limits or stops the forward movement ofdrill bit 180. The chuck assembly 140 removably retains drill bit 180for rotary motion at a surgical site. Drill bit 180 can be selectivelyattached to and detached from the chuck assembly 140 by the medicalpractitioner. Chuck assembly 140 has a release collar 141. Manualmovement of the release collar 141 in a proximal direction causes thechuck assembly to release an inserted drill bit 180. Releasing therelease collar 141 causes a coil spring 143 to bias the release collarin a distal direction resulting in the inserted drill bit 180 beinglocked in chuck assembly 140.

A more detailed understanding one version of how the motor internal tohandpiece 102 operates is found in the Applicant's Assignee's U.S. Pat.No. 7,638,958, issued 29 Dec. 2009, the contents of which are explicitlyincorporated herein by reference. It should be understood that the exactstructure of the portions of the motor that produce the rotational poweris not part of this or the other versions of this invention. Thestructure of the motor in this version and the other versions of theinvention is relevant in so far as certain motor components are featuresof this invention that facilitate the selective stopping of penetrationof bone by drill bit 180.

II. Rotary Surgical Drill with Top Mounted Brake Mechanism Having anExternal Telescoping Rack

A. Brake Mechanism

With reference to FIG. 4, brake mechanism 200 mounted to the top side ofhandpiece 102 is shown. The brake mechanism 200 comprises a linearactuator 250 and a telescoping rack, bar or rod 360 that are mounted inan actuator housing 204. Actuator housing 204 is mounted to handpiece102. Specifically, the actuator housing 204 is mounted to case 103toward proximal end 107 and rearward of handle 104. The actuator housing204 extends upwardly above case 103.

Turning to FIGS. 6A-6D, details of the actuator housing 204 areillustrated. The actuator housing 204 has a C-shaped body 206 that isformed with a pair of generally parallel opposed arms 208 that extendaway from a central body 206. Body 206 and arms 208 define a passage 209that extends through housing 204. The bottom side of body 206 has asurface 207 that faces passage 209. The arms 206 terminate in opposedribs 210 that angle inwardly into passage 209. Apertures 212 are formedin the lower most portion of each arm 208. The apertures 212 aredimensioned to receive screws 214. The screws 214 hold the housing 204to handpiece 102. A cylindrical shaped boss 216 is attached to body 206and extends perpendicularly in an upward direction away from body 206.The boss 216 is formed with a bore 218 that is defined by an innerannular surface 220. Internal threads 222 are defined in inner annularsurface 220. The actuator housing 204 can be formed from suitablematerials such as a metal.

The bore 218 extends downwardly into boss 216 and terminates in a bottomwall 224. A cable slot 225 is defined in bottom wall 224 and extendsthrough the bottom wall 224. Two spaced apart circular holes 226 alsoextend through bottom wall 224 and are contiguous with passage 209. AD-shaped aperture 228 extends through bottom wall 224 and is contiguouswith passage 209. A counter-bore 230 surrounds each of the holes 226 andextends from surface 207 partially into body 206.

An elongated tube 232 has a proximal end 233 that is connected to adistal face of body 206 and a distal terminal end 234. A square shapedlumen 236 extends entirely through tube 232 and also entirely throughbody 206. The lumen 236 is defined by four orthogonal inner walls 238that extend along the length of lumen 236. A projection 239 (FIG. 5B)extends upwardly from the bottom wall 238 slightly into lumen 236towards the proximal end of the housing.

The actuator housing 204 is mounted to handpiece 102. Housing 204 isplaced over upper housing 103 with arms 208 surrounding upper housing103 and housing inner surface 207 resting against upper housing 103. Theupper housing 103 includes threaded holes 240 (FIG. 4). The screws 214(FIG. 4) extend through housing apertures 212 and are received bythreaded holes 240 thereby securing actuator housing 204 to handpiece102.

The linear actuator 250 comprises an actuator or solenoid 252 and apiston or plunger 280. Solenoid 252, described with reference to FIGS.7A and 7B, is generally cylindrical in shape and has a top surface 254,a lower surface 256 and a circumferential outer surface 258. Acounter-bore 260 extends downwardly from top surface 254 into solenoid252 and terminates in a bottom wall 262. A bore 264 is defined throughwall 262. Bore 264 extends between bottom wall 262 and lower surface256. A pair of cylindrical pins 266 extend perpendicularly away fromlower surface 256 and are located on opposite sides of bore 264. Thesolenoid 252 has internal wire windings (not shown) that, when energizedby an electrical current, create a magnetic field. The wire windings areconnected to terminals 268 that are mounted in a connector 270 on theouter surface 258. The terminals 270 are connected to respective circuitlines at end 275 of a flexible cable 274 (FIG. 5A) using suitabletechniques such as soldering.

With additional reference to FIGS. 5A and 5B, the solenoid 252 ismounted into the bore 218 of the housing such that the solenoid bottomsurface 256 is adjacent to and resting on bottom wall 224 (FIG. 6C) andthe pins 266 extend into and are retained in housing holes 226. In oneembodiment, holes 226 and pins 266 are dimensioned such that pins 266are press fit into holes 226. The solenoid circumferential outer surface258 is surrounded by the housing inner surface 224. The flexible cable274 extends from solenoid 252 and is routed through cable slot 225 (FIG.6C) in bottom wall 224. The other end 276 of flexible cable 274 iselectrically connected to terminals 277 (FIG. 4) located on handpieceupper housing 103. Terminals 277 are electrically connected to PCB 118(FIG. 3). Solenoid 252 is therefore electrically connected to PCB 118via flexible cable 274.

Referring now to FIGS. 8A and 8B, the plunger 280 includes a centralcylindrical shaped hub 282 that has an upper end 284 and a lower end286. A disc shaped flange 288 extends outwardly from the upper end 284.A cylindrical shaped post 290 extends perpendicularly away from theflange 288. Post 290 has a terminal section 292 that has a diameter thatis less than the remainder of post 290. External threads 294 are definedon terminal section 292. A cylindrical shaped shaft 296 extendsperpendicularly away from the hub lower end 286. The shaft 296 has aD-shaped terminal section 298 that is partially defined by a flatsurface 300. D-shaped terminal section 298 terminates at an end 302. Agear tooth 304 extends outwardly from end 302. Gear tooth 304 is shapedto engage with teeth in telescoping rack 360 as will be described later.In one embodiment, the plunger 280 is formed from a Ferro-magneticmaterial such as steel that is attracted to a magnetic field.

With additional reference to FIGS. 5A and 5B, plunger 280 is mountedwithin solenoid 252. The plunger hub 282 is received into the solenoidbore 260 with the cylindrical shaft portion 296 extending through bore264. The D-shaped section 298 further extends into and is received bythe D-shaped aperture 228 of housing 204. A washer 306 is mounted overplunger hub 282 and rests against the bottom face of flange 288. Theplunger flange 288 extends over the top surface 254 of solenoid 252 andis slightly spaced from top surface 254.

Turning to FIGS. 9A and 9B, features of cover 320 are illustrated. Cover320 is cylindrical in shape and has a top side 321 and a bottom side322. A circular collar 324 extends perpendicularly away from top side321. A bore 325 is defined in collar 324. Bore 325 terminates in a wall326. External threads 327 are defined on the outer surface of collar324. An aperture 328 is defined through the center of wall 326 and iscontiguous with bore 325. Another circular collar 330 extendsperpendicularly away from the bottom side 322. Collar 330 has a largerdiameter than collar 324. A bore 331 is defined in collar 330. The bore331 terminates at bottom side 322. External threads 332 are defined onthe outer surface of collar 330. Cover 320 can be formed from injectionmolded plastic or metal.

Referring to FIGS. 10A and 10B, features of cap 340 will now bedescribed. The cap 340 is cylindrical in shape and has a top side 342and a lower side 344. A bore 346 extends from lower side 344 partiallyinto cap 340. Internal threads 348 are defined on the inner surface ofbore 346.

With additional reference to FIGS. 5A and 5B, cover 320 is attached toactuator housing 204. Cover 320 encloses the linear actuator 250 ofsolenoid 252 and plunger 280. The cover 320 is screwed into housing 204such that the cover external threads 332 are mated with the housinginternal threads 222. The cover 320 extends over the top side of flange288 such that flange 288 is juxtaposed to the bottom side 322 of cover320. The cylindrical post 290 of plunger 280 extends upwardly throughthe cover aperture 328.

A coil spring 350 is located in cover bore 325 and surrounds the plungerpost 290. A nut 352 is threaded onto the threads 294 (FIG. 8B) of post290 in order to retain coil spring 350 to post 290. The coil spring 350is compressed between nut 352 and wall 326 of cover 320. The coil spring350 biases the plunger 280 in an upward direction away from solenoid252. The cap 340 is screwed onto cover 320 such that the cover externalthreads 327 are mated with the cap internal threads 348. The cap 340completes a sealed enclosure for linear actuator 250.

A space or gap 354 (FIG. 5B) is defined between the bottom side 322 ofcover 320 and the top surface 254 of solenoid 252. The flange 288 ofplunger 280 can move in gap 354 between a first position when solenoid252 is de-energized or turned off and coil spring 350 biases the flange288 into contact with the bottom side 322 of cover 320. When solenoid252 is energized or turned on, the magnetic field generated by solenoid252 attracts the steel flange 288 and overcomes the spring force of coilspring 350, thereby moving flange 288 into contact with the top surface254 of solenoid 252.

FIG. 11 illustrates features of telescoping rod or rack 360. Telescopingrack 360 can be formed from suitable materials such as metal. Rack 360is generally elongated in length and has a center section 362, aproximal end 364 and a distal end 366. Rack 360 has a squarecross-sectional profile that is defined by four orthogonal sides 368. Alinear measurement scale or depth gauge 370 is affixed to one or moresides 368 of rack 360 within center section 362. The linear measurementscale 370 can include graduated marks and indicia such as numbers. Markson the linear measurement scale correspond to the length of the drillbit that extends beyond the end of the tissue protector. The depth gauge370 is used to measure the length of drill bit 180 that is inserted intoa bore. In one embodiment, measurement scale 370 can be graduated inmillimeters. Depth gauge 370 is read where rack 360 enters tube 232 atthe intersection of depth gauge 370 and the tube distal end 234.

The rack 360 further has a proximal section 372 with a roundcross-sectional shape that is located toward the proximal end 364. Astep 373 is defined where center section 362 and proximal section 372intersect.

A set of gear teeth 374 are formed in the upper side of the proximalsection 372 and extend along the length of proximal section 372 betweencenter section 362 and proximal end 364. The teeth 374 are dimensionedsuch that tooth 304 (FIG. 8B) can mate with and be engaged with teeth374. An arm 376 is attached to the distal end 366 of rack 360. The arm376 angles downwardly and away in a distal direction from distal end366. An annular ring 378 is attached to arm 376. The ring 378 has aproximal face 380, a distal face 382 and a circumferential outer sidesurface 384. The arm 360 is attached to proximal face 380. A circularopening 386 extends through ring 378.

Turning to FIG. 5B, the rack 360 is further formed with a threaded bore388 that extends from proximal end 364 partially into proximal section372. The bore 388 receives a screw 390. The head of screw 390 abuts theproximal face of housing 204. Screw 390 prevents the removal of rack 360from housing 204 after the rack is inserted into lumen 236.

Referring additionally to FIGS. 4, 5A, 5B and 6A, rack 360 is mounted inlumen 236 for telescoping or sliding movement. Rack 360 can slide ortelescope in a linear manner in proximal and distal directions relativeto actuator housing 204. A coil spring 392 is located in lumen 236partially surrounding the center section 362 of rack 360. The distal endof the coil spring 392 rests against step 373 and the proximal end ofcoil spring 392 rests against a projection 239 (FIG. 5B) that extendsinto lumen 236. The coil spring 392 biases rack 360 in a distaldirection away from handpiece 102.

Returning to FIG. 11, a digital caliper or second depth gauge 400 ismounted to upper housing 103. Digital caliper 400 can be attached toupper housing 103 using fasteners (not shown). Digital caliper 400 iscommercially available. Digital caliper 400 has U-shaped groove thatreceives and is mounted over a portion of tube 232. Digital caliper 400has a digital display 404 that is calibrated to the position of rack 400relative to handpiece 102. Digital caliper 400 can sense the position ofrack 360 and provide a numerical readout of a distance that rack 360 isextended from or inserted into digital caliper 400 which corresponds toa measure of the length of drill bit 180 that is inserted into a bonebore.

With reference to FIGS. 12A and 12B, a tissue protector 420 positionedaround drill bit 180 is shown. Drill bit 180 has a center section 181, asquare shaped proximal drive head 182, and a distal pointed cutting tip183. The square shaped proximal drive head 182 is clamped within chuckassembly 140 holding drill bit 180 to chuck assembly 140. Drive head 182receives rotary torque from chuck assembly 140 in order to rotate drillbit 180. Grooves 184 are defined in the center section 181 of drill bit180 by edges 185. The drill bit 180 has an outer circumferential surface186.

The tissue protector 420 is generally cylindrical in shape. Tissueprotector 420 is formed with a hollow sleeve 424 that defines aninterior passage 426. The sleeve 424 has an outer surface 425. Thepassage 426 extends through the entire length of tissue protector 422.The tissue protector 420 has a proximal end 428 and a distal end 430. Aflange 432 extends outwardly and surrounds the proximal end 428 oftissue protector 420. Flange 432 has an outer annular surface 434.

The tissue protector 420 is attached into the opening 386 (FIG. 11) ofring 378 (FIG. 11). Specifically, flange 432 has external threads (notshown) on the outer annular surface 434 that mate with internal threads(not shown) that face into ring opening 386. The tissue protector 420 iscoupled to rack 360 via ring 378. The tissue protector 420 is slid overthe outer circumference of drill bit 180. The interior diameter ofpassage 426 is larger than the diameter of drill bit 180 such thattissue protector 420 can slide relative to drill bit 180 along thelength of dill bit 180. Sleeve 424 is dimensioned to have aninterference fit to the outer circumference surface 186 of drill bit180. Drill bit 180 can slide along the inner circumference of sleeve 424in a distal direction as a bore is formed by drill bit 180.

During the operation of rotary surgical drill 100, as the drill bit 180moves in a distal direction relative to the static tissue protector 420during drilling, the length of the drill bit exposed or extending beyonddistal tip 430 increases. During formation of a bore by drill bit 180,the distal end 430 of the tissue protector 420 is in contact with aproximal surface of the tissue (bone) adjacent the bore being formed andremains static. When the tissue protector 420 is moved in a distaldirection relative to drill bit 180, the length of the drill bit exposedor extending beyond the distal end 430 of the tissue protectordecreases.

B. Controller

FIG. 13 illustrates a schematic diagram of the electrical componentswithin surgical drill 100 that are connected to controller 450.Controller 450 controls the operation of rotary surgical drill 100.Controller 450 also controls the operation of braking mechanism 200. Thecontroller 450 comprises a processor 452, memory 454 and input/output(I/O) interface or controller 456. Processor 452 is in communicationwith memory 454 and input/output interface 456 via one or morecommunication buses 458. Controller 450 is mounted to PCB 118 (FIG. 3)within handpiece 102.

Processor 452 is a suitable microprocessor, field programmable gatearray or an application specific integrated circuit. One or more sets ofinstructions or software are stored on a machine-readable medium ormemory 454 that embodies any one or more of the methods or functionsdescribed herein. Memory 454 is a random access memory (RAM) or anonvolatile random access memory such as NAND flash memory or any othersuitable memory. Processor 452 can also contain memory that leastpartially stores programs within processor 452 during execution thereof.Memory 454 stores firmware/software/programs that at least partiallycontrol the operation of rotary surgical drill 100. In one embodiment,the controller 450 is a single integrated circuit.

The term “memory or machine-readable medium” shall also be taken toinclude any medium that is capable of storing, encoding or carrying outa set of instructions for execution by the processor and that cause theprocessor to perform any one or more of the methodologies shown in thevarious embodiments of the present invention. Machine-readable medium ormemory shall accordingly be taken to include, but not be limited to,solid-state memories, optical and magnetic media, and carrier wavesignals.

The I/O interface or controller 456 provides the required timing, signallevels and protocols to allow processor 452 to communicate withcomponents external to controller 450. I/O interface 456 is incommunication with external components through several electrical cablesor wires 460. I/O interface 456 is in communication with triggerswitches 116, 117 and a motor driver 462. The motor driver 462 is acircuit that provides the proper current and voltage levels to powerelectric rotary motor 122. The electric rotary motor 122 is a variablespeed electric motor that rotates chuck assembly 140 and drill bit 180.

A sensor 464 is in communication with I/O interface 456. Sensor 464 canbe one of a variety of sensors that sense operating conditions andparameters of rotary surgical drill 100. In one embodiment, sensor 464is a Watt and current sensor that senses the Watts consumed and currentdrawn by motor 122 and provides an electrical signal that corresponds tothe voltage and current drawn by motor 122. In another embodiment,sensor 464 is a rotation sensor that senses the number or revolutionsper minute (RPM) that motor 122 turns. The rotation sensor can be a Halleffect sensor that counts the number of revolutions of rotor 124. Therotation sensor provides an electrical signal that corresponds to theRPM of motor 122. In one more embodiment, sensor 464 is a torque orforce sensor that senses torque on one or one or more components ofrotary surgical drill 100 and provides an electrical signal thatcorresponds to the torque reading. For example, sensor 464 can be astrain gauge that is mounted to motor shaft 130 and is in electricalcommunication with I/O interface 456.

I/O interface 456 is also in communication with solenoid 252. Processor452 can cause solenoid 252 to turn on (energized) or turn off(de-energized). Processor 450 is further in communication with digitalcaliper 400 and with a power supply or battery 150 through I/O interface456. Digital caliper 400 can transmit a digital signal to processor 452that indicates the depth of the drill bit in a bone bore. Battery 150provides the electrical power necessary to power controller 450 andmotor 122. In one embodiment, controller 450 is mounted to PCB 118 (FIG.3) within chamber 105 (FIG. 3) of handle 104 (FIG. 3).

The memory 454 can store a variety of data, sets of instructions,software, firmware, modules, programs or utilities for execution byprocessor 452 and that cause processor 452 to perform any one or more ofthe functions and methods herein described. Memory 454 comprises abraking module 470, sensor parameter threshold values 472 and data 474.Braking module 470 is a program that determines when to stop the forwardtravel of drill bit 180 via the actuation of solenoid 252 based on inputfrom sensor 464. Braking module 470 controls the operation of brakingmechanism 200. The sensor parameter threshold values 472 arepre-determined values of sensor parameters that processor 452 uses todetermine when to turn solenoid 252 on and off. In one embodiment,threshold values 472 can be when the motor current drops below apre-determined level within a pre-determined time period. For example,if the motor current drops below 20 milli-amps within a 15 milli-secondperiod, processor 452 can turn on solenoid 252 causing the engagement ofbraking mechanism 200. Data 474 can store various operating parametersand conditions of rotary surgical drill 100 such as the number of RPMsand the total usage time of the drill. Data 474 can also keep a log ofsensor values over time as detected by sensor 464.

FIG. 13 and the accompanying discussion are intended to provide ageneral description of an exemplary controller or processor adapted toimplement the described embodiments. While embodiments will be describedin the general context of instructions residing on memory stored withina controller, those skilled in the art will recognize that embodimentsmay be implemented in a combination of program modules running in anoperating system. Generally, program modules include routines, programs,components, and data structures, which perform particular tasks orimplement particular abstract data types.

C. Operation

The rotary surgical drill 100 is used at a surgical site by a medicalpractitioner. The medical practitioner grasps handle 104 and directs thedrill bit tip 183 to the surgical site. Drill bit 180 is used to drillone or more bores into a bone. In one embodiment, a screw can beinserted into the bore.

With reference to FIGS. 1 and 5B, initially, solenoid 252 is turned offby controller 450 such that spring 350 biases plunger 280 to an uppermost position where tooth 304 is disengaged from the teeth 374 of rack360. In this position, rack 360 is free to telescope or slide withinlumen 236. Because rack 360 is coupled to tissue protector 420,displacement of tissue protector 420 relative to drill bit 180 causes alike displacement of rack 360. Initially, the tissue protector 420 ismanually positioned by a medical practitioner so the distal end 430 ofthe tissue protector is slightly drawn back from the drill bit distaltip 183. Only the bit distal tip 183 is exposed as seen in FIG. 1. Themedical practitioner slides tissue protector 420 relative to drill bit180 by overcoming the interference fit between tissue protector sleeve424 and drill bit 180. Also initially, the drill bit 180 is notsubjected to any axial loading. Axial loading is defined as a forceacting along the same axis as the longitudinal axis of drill bit 180.

In the following discussion of FIGS. 14A-14C, reference is also made tocomponents shown in FIGS. 1, 11, 12A, 12B and 13. Turning to FIG. 14A,surgical drill 100 is used at a surgical site 488 to form a bore in abone. The drill bit 180 is positioned against the proximal side 492 ofthe bone 490 where the bone bore 498 is to be formed. The drill bit 180is forced downwardly by the medical practitioner in an axial direction.After the drill bit 180 is so positioned, the rotary surgical drill 100is actuated in a forward or clockwise rotation (as viewed from behindthe handpiece) by the depression of trigger switch 116. Trigger switch116 causes controller 450 to rotate motor 122 within handpiece 102 andto rotate the chuck assembly 140 and drill bit 180. The combination ofthe rotating drill bit and the axial load placed on the drill bitresults in the cutting edges of the drill bit tip 183 cutting the bone490 so as to form a bore 498. During formation of the bone bore, themotor 122 will draw a relatively high level of current in order to keepa desired number of revolutions per minute (RPM) of the drill bit 180.The motor 122 uses the relatively high level of current in order toovercome the frictional force created by the drill bit 180 rubbingagainst the bone 490. The current and voltage levels drawn by motor 122is measured by sensor 464 and transmitted as an electrical signal tocontroller 450.

Referring to FIG. 14B, as the drill bit tip 183 enters the bone, thedistal end 430 of tissue protector 420 abuts the proximal side 492 ofbone 490 limiting the forward movement of tissue protector 420. As thedrill bit 180 continues to rotate, the combination of the rotating drillbit and the axial load placed on the drill bit by the medicalpractitioner overcomes the interference fit between tissue protector 420and the outer circumference 186 of the drill bit resulting in the tissueprotector 420 remaining static against the bone 490 while the drill bitslides through the interior passage 426 of sleeve 424. As the bone bore498 is formed, the length of the drill bit 180 exposed or extendingbeyond the distal end 430 of tissue protector 430 increases. Statedanother way, as the drill bit and by extension the handpiece 102advance, the distance between the distal end of the tissue protection420 and the handpiece decrease. Continued rotation of the drill bit andaxial loading causes the drill bit tip 183 to penetrate through the boneand bone marrow 496 and to approach the distal side 494 of bone 490.

With reference to FIG. 14C, eventually, the drill bit tip 183 boresthrough the distal side 494 of bone 490 in which the bone bore 498 isbeing formed. When the drill bit bores through the distal side 494 ofbone 490, the frictional force created by the drill bit 180 rubbingagainst the bone 490 suddenly decreases. The current drawn by motor 122also rapidly decreases and the RPM of the drill bit 180 rapidlyincreases. The sudden drop in the current drawn by the motor over a timeperiod is measured or sensed by sensor 464 and the current informationis transmitted as an electrical signal to controller 450. In oneembodiment, the change in current or current drop over a time period canhave units of milliamps per second. Processor 452, which is executingbraking module software 470, compares the received change in currentdata from sensor 464 to a pre-determined threshold change in current orcurrent drop level that is stored in sensor parameter threshold values472.

In response to the received change in current from sensor 464 beinggreater than the stored threshold change in current level, processor 452triggers the engagement of braking mechanism 200 by turning on solenoid252. When solenoid 252 is turned on, the magnetic field generated bysolenoid 252 attracts the steel flange 288 and overcomes the springforce of coil spring 350, thereby moving flange 288 and the attachedplunger 280 downwardly until flange 288 contacts with the top surface254 of solenoid 252. At the same time, the downward movement of plunger280 forces gear tooth 304 into engagement with gear teeth 374 of rack360, thereby locking rack 360 to handpiece 102. When gear tooth 304 isengaged with gear teeth 374, handpiece 102 is no longer able to advancetowards tissue protector 420. By extension this prevents furtheradvancement of the drill bit 180 beyond the distal side 494 of the bone490. Any additional rotation of drill bit 180 or application of axialforce does not result in further advancement of drill bit 180 due to theabutment of tissue protector 420 against the proximal side 492 of thebone. Drill bit 180 is thus prevented from further advancement beyonddistal side 494 thereby avoiding the cutting any tissue 497 adjacent tothe distal side 494 of the bone 496.

The length of the drill bit inserted into the bone bore 498 is equal tothe distance between the distal end 430 of tissue protector 420 and thedistal tip 183 of drill bit 180. This length is the approximate lengththat is required for a bone screw that is to be inserted into the bonebore by the medical practitioner. The linear measurement scale or depthgauge 370 that is affixed to one or more sides 368 of rack 360 iscalibrated to correspond to the length of the drill bit 180 that extendsbeyond the distal end 430 of tissue protector 420. The length of thedrill bit in the bone bore can be read by the medical practitioner whererack 360 enters tube 232 at the intersection of depth gauge 370 and tubedistal end 234.

The length of the drill in the bone bore 398 can also be read fromdigital caliper 400. Digital caliper 400 is calibrated to correspond tothe length of the drill bit 180 that extends beyond the distal end 430of tissue protector 420. The length of the inserted drill bit can beread by a medical practitioner on digital display 404 of digital caliper400. Therefore, the length of a bone screw required for insertion intobone bore 498 can be read from either depth gauge 370 or from digitalcaliper 400. Depth gauge 370 and digital caliper 400 allow for thecorrect length of bone screw to be selected by the medical practitionerto match the depth of the bone bore. Depth gauge 370 and digital caliper400 can assist in preventing bone screws that are too long or too shortfrom being selected for use.

The medical practitioner may elect to pull the drill bit 180 out fromthe bone bore before reading depth gauge 370 or digital caliper 400.However, if the bone bore is deep, the fit between the drill bit and thebone bore can be a particularly tight fit. The medical practitioner canrotate drill bit 180 in a reverse (counterclockwise) direction usingreverse trigger switch 117 in order to disengage drill bit 180 from thebone bore. Alternatively, with the drill bit 180 removed from the bonebore, the medical practitioner can place bone screws adjacent the drillbit portion that extends beyond the tissue protector 420. Thepractitioner then visually selects the bone screw that matches the depthof the bone bore.

Before the medical practitioner uses rotary surgical drill 100 to formanother bore, braking mechanism 200 is disengaged. In one embodiment,processor 452 turns off solenoid 252 after sensing the depression ofreverse trigger switch 117. In another embodiment, processor 452 turnsoff solenoid 252 after detecting a certain sequence of depression of thetrigger switches 116, 117. For example, processor 452 can turn offsolenoid 252 after detecting the simultaneous depression of both triggerswitches 116 and 117. In an additional embodiment, a separate switch(not shown) can be provided to turn off solenoid 252. After solenoid 252is turned off, spring 350 biases plunger 280 to move in an upwarddirection causing disengagement of gear tooth 304 from teeth 374. Therack 360 is now free to slide relative to handpiece 102 and drill bit180.

The braking mechanism 200 of the present invention using solenoid 252,plunger 280, rack 360 and tissue protector 420 allows a drill bit 180forming a bone bore to stop further penetration beyond the bone afterthe initial penetration through the bone, thereby preventing damage toany tissue adjacent the distal side of the bone.

The depth gauge 370 and digital caliper 400 allow for the correct lengthof bone screw to be selected by the medical practitioner to match thelength of the bone bore.

Referring to FIG. 15, a flowchart of a method 480 of operating rotarysurgical drill 100 (FIG. 1) is shown. Method 480 illustrates anexemplary method by which the rotary surgical drill 100 presented withinthe preceding figures performs different aspects of the processes thatenable one or more embodiments of the disclosure. Method 480 isdescribed specifically as being performed using rotary surgical drill100 and controller 450. The description of method 480 is provided withgeneral reference to the specific components illustrated within thepreceding figures.

Method 480 begins at block 482 where processor 452 executing brakingmodule 470 monitors in real time the voltage and current drawn by rotaryelectric motor 122 during forward rotation of motor 122. As the drillbit 180 is being rotated by motor 122, the current drawn by motor 122will vary depending upon the load on motor 122. Processor 452 monitorsthe voltage and current drawn over time via an electrical signaltransmitted from one or more sensors 464.

At decision step 484, processor 452 compares the change in the presentcurrent value for a period of time from sensor 464 to a pre-determinedthreshold value stored in sensor parameter threshold values 472 anddetermines if the change in current for a period of time is greater thanthe stored threshold value 472. A sudden drop or change in the currentdrawn by the motor 122 during a time period indicates that the drill bithas completed cutting through the bone.

In response to the change in current for a period of time not beinggreater than the stored threshold value 472, method 480 returns to block482 where processor 452 continues to monitor the voltage and currentdrawn by rotary electric motor 122 during forward rotation of motor 122.

In response to the change in current for a period of time being greaterthan the stored threshold value 472, processor 452 triggers theengagement of braking mechanism 200 by turning on solenoid 252 at block486. When solenoid 252 is turned on, the magnetic field generated bysolenoid 252 attracts the steel flange 288 and overcomes the springforce of coil spring 350, thereby moving flange 288 and the attachedplunger 280 downwardly until flange 288 contacts with the top surface254 of solenoid 252. At the same time, the downward movement of plunger280 forces gear tooth 304 into engagement with teeth 374 of rack 360,locking rack 360 to handpiece 102. When gear tooth 304 is engaged withteeth 374, drill bit 180 cannot be advanced relative to tissue protector420, thereby preventing any further advancement of drill bit tip 183beyond the distal side 494 of bone 490. Any additional rotation of drillbit 180 or application of axial force by the medical practitioner doesnot result in further advancement of drill bit 180.

The actuation of solenoid 252 stops the movement of rack 360 relative tohandpiece 102 and also results in a like cessation of the axialadvancement of drill bit 180. Therefore, after the drill bit 180 has cutthrough the bone 290, drill bit 180 is prevented from furtheradvancement beyond distal side 494 thereby avoiding cutting any tissueadjacent to the bone bore. Method 480 then ends.

III. Rotary Surgical Drill with End Mounted Brake Having an ExternalTelescoping Rack

FIGS. 16-19 illustrate another embodiment of a rotary surgical drill 500that has an end mounted brake mechanism 520. Rotary surgical drill 500comprises a handpiece 102, chuck assembly 140, drill bit 180, controller450 and brake mechanism 520. Rotary surgical drill 500 shares many ofthe same components as rotary surgical drill 100 of FIG. 1. In thediscussion of rotary surgical drill 500, components that are common torotary surgical drill 100 will be referred to using the same referencenumbers.

Rotary surgical drill 500 includes handpiece 102 that contains therotary electric motor 122. Handpiece 102 of FIGS. 16-19 is the same asthe previously described handpiece 102 of FIG. 1, except that anelongated sleeve 502 has been added to the top of case or upper housing103. In one embodiment, sleeve 502 is integrally formed with case orupper housing 103. Sleeve 502 is parallel to the axis of case 103 andhas a proximal end 504 and a distal end 506. An elongated round lumen508 is defined within the interior of sleeve 502 and extends the entirelength of sleeve 502. Lumen 508 is dimensioned to receive the proximalend of rack 360. A V-shaped opening 510 is formed toward the center ofsleeve 502. The V-shaped opening 510 is dimensioned to receive amagnifying lens 512 that includes a measurement line or indicator line514. The measurement line 513 is oriented perpendicular to the axis ofsleeve 502.

A. Brake Mechanism

End mounted brake mechanism 520 is mounted to the proximal end 107 ofcase or upper housing 103. End mounted brake mechanism 520 comprises alinear actuator 250 and a telescoping rack or rod 360 that are mountedin an actuator housing 524. Actuator housing 524 is mounted to handpiece102. Specifically, the actuator housing 524 is mounted to upper housing103 adjacent to proximal end 107 by screws 526 (FIG. 18).

Turning to FIGS. 21, 22 and 23, details of the actuator housing 524 willnow be described. The actuator housing 524 can be formed from suitablematerials such as machined metal. Actuator housing 524 is generallyrectangular in shape and has a central body 528. Housing 524 has aproximal end 530 and a distal end 532. Central body 528 is defined byfour orthogonal sides 534 that have orthogonal outer surfaces 536 andorthogonal inner surfaces 538. Inner surfaces 538 define an interioractuator cavity 540 that opens in a proximal direction. A proximal face542 is located on the proximal end of sides 534. The actuator cavity 540terminates at a dividing wall 544. Wall 544 has a center thru bore 546and a counter bore 548 that is defined by a step 550. Counterbore 548faces into actuator cavity 540.

A pair of diametrically opposed grooves 552 are formed on the innersurfaces 538 of opposed vertical sides 534. Grooves 552 extend fromproximal face 542 partially towards wall 544. An aperture 554 is definedin the horizontal bottom side 534. A pair of diametrically opposed holes556 are defined through wall 544 on opposite sides of counterbore 548.Another hole 558 is defined through wall 554 above one the holes 556.Four apertures 560, 561, 562 and 563 are formed through horizontal topside 534.

An elongated tube 566 is formed with and located above the tophorizontal side 534. Tube 566 extends the length of actuator housing 524and has a proximal end 567 and a distal end 568. A lumen 570 extendsentirely through tube 566. A projection 571 (FIG. 20) extends downwardlyfrom the upper inner surface defined by lumen 570 slightly into lumen570. Lumen 570 is dimensioned so as to receive the proximal end of rack360. The hole 562 is contiguous with lumen 570 such that an opening isformed between interior cavity 540 and lumen 570. A gear slot 572 isdefined in the base of tube 566 towards distal end 567.

A D-shaped wall 574 extends perpendicularly away from the distal face ofdividing wall 544. Wall 574 has an outer surface 575. The terminal endof wall 574 has a protruding lip 576 that extends away therefrom.

The actuator housing 524 is mounted to proximal end 107 of upper housing103. The D-shaped wall 574 is positioned within the interior of upperhousing 103 in an overlapping relationship with proximal end 107. Withadditional reference to FIG. 18, a cover 580 is mounted over actuatorcavity 544 and the proximal face 542 of actuator housing 524. Cover 580can be formed from injection molded plastic or machined metal. Cover 580has a pair of diametrically opposed holes 582 that extend through cover580. Screws 526 hold cover 580 and actuator housing 524 to upper housing103 of handpiece 102. Screws 526 extend through holes 582, actuatorcavity 540, holes 556 and are received in threaded bores (not shown) inthe proximal end 107 of upper housing 103.

Turning to FIGS. 18, 20 and 22, the linear actuator 250 is mountedwithin actuator cavity 540. Solenoid 252 is mounted in cavity 540 suchthat the solenoid bottom surface 256 is adjacent and resting on theinner surface of top side 534 and pins 266 extend into and are retainedin apertures 560 and 561. In one embodiment, apertures 560, 561 and pins266 are dimensioned such that pins 266 are press fit into holes 560,561. The flexible cable 274 extends from solenoid 252 and is routedthrough bore 546. The other end 276 of the flexible cable 274 iselectrically connected to terminals (not shown) located in handpieceupper housing 103. The terminals on end 276 are electrically connectedto PCB 118. The plunger 280 is mounted in solenoid 252. Plunger hub 282is mounted in solenoid bore 260 with the cylindrical shaft portion 298extending through bore 562. A washer 306 is mounted over plunger hub 282and rests against the bottom face of flange 288. The plunger flange 288extends over the surface 254 of solenoid 252.

A planar rectangular spring plate 590 has ends 591 and 592 and a centerrecess 594. Ends 591 and 592 rest in and are supported by housinggrooves 552. The spring plate 590 spans across the width of cavity 540extending between the interior faces of vertical side walls 534. A coilspring 350 surrounds plunger post 290. A nut 352 is threaded onto thethreads 294 (FIG. 8B) of post 290. The coil spring 350 is compressedbetween nut 352 and the bottom side of spring plate 590. Coil spring 350biases plunger 280 in a downward direction away from solenoid 252.

A space or gap 354 (FIG. 20) is defined between the top side of springplate 590 and the bottom surface 254 of solenoid 252. The flange 288 ofplunger 280 can move in gap 354 between a first position when solenoid252 is de-energized or turned off and coil spring 350 biases flange 288into contact with the top side of spring plate 290. When solenoid 252 isenergized or turned on, the magnetic field generated by solenoid 252attracts the steel flange 288 and overcomes the spring force of coilspring 350, thereby moving flange 288 into contact with the bottomsurface 254 of solenoid 252.

With reference to FIG. 24 additional features of telescoping rod or rack360 used with rotary surgical drill 500 are shown. Telescoping rack 360is the same as previously described with reference to rotary surgicaldrill 100 except that gear teeth 374 have been moved from the tophorizontal side 368 of proximal section 372 to the bottom horizontalside 368 of proximal section 372 and depth gauge teeth 598 have beenadded to one of the vertical sides 368 of proximal section 372. Depthgauge teeth 598 are positioned above gear teeth 374.

Rack 360 is mounted in lumen 508 within sleeve 502 and in lumen 570within tube 566 for telescoping or sliding movement. With reference toFIGS. 16, 17 and 20, rack 360 can slide or telescope in a linear mannerin proximal and distal directions relative to upper housing 103 andactuator housing 524. A coil spring 392 is located in lumen 508partially surrounding the center section 362 of rack 360. The distal endof the coil spring 392 rests against step 373 (FIG. 24) and the proximalend of the coil spring 362 rests against projection 571 (FIG. 20) thatextends into lumen 570. Coil spring 392 biases rack 360 in a distaldirection away from handpiece 102. During assembly, coil spring 392 isplaced over proximal end 364 and the proximal end 364 is inserted intothe distal opening of lumen 508. Rack 360 is formed with a threaded bore388 that extends from proximal end 364 partially into proximal section372. Bore 388 receives a screw 390 after rack 360 has been inserted intolumen 570. When rack 360 moves in a distal direction, eventually thehead of screw 390 will abut the projection 571 within lumen 570. Screw390 prevents the removal of rack 360 from housing 524 and lumen 508.

Referring to FIGS. 16 and 24, a linear measurement scale 370 is affixedto one or more sides 368 of rack 360 within center section 362. Linearmeasurement scale 370 can include graduated marks and indicia such asnumbers. Measurement scale 370 can be used to measure the length of thedrill bit 180 that is inserted into a bone bore. Measurement scale 370is read through magnifying lens 512. Measurement scale 370 is read atthe intersection of measurement line or indicator line 514 withmeasurement scale 370. Magnifying lens 512 magnifies the indicia onmeasurement scale 370 for easier reading by the medical practitioner.

An additional or second depth gauge 600 is positioned on the top side534 of actuator housing 524. Depth gauge 600 comprises gear 610 and rack360. Turning to FIGS. 16, 24 and 25, depth gauge 600 includes a depthgauge gear 610 and a shoulder screw 630. Depth gauge gear 610 has teeth612 formed on the outer circumference of gear 610. Measurement indicia614 such as numbers are disposed on the top surface 616 of gear 610.Shoulder screw 630 has a head 632 and a shaft 634 with external threads636. Gear 610 is mounted above the top side 534 of actuator housing 524.Shoulder screw 630 extends through a hole in gear 610 and into threadedhole 563 (FIG. 21). Threads 636 mate with the threads of hole 563. Gear610 is free to rotate about shoulder screw 630.

The gear teeth 612 extend into and through housing slot 572 (FIG. 21)and into engagement with the depth gauge teeth 598 on the side of rack360. The linear movement of rack 360 causes depth gauge teeth 598 torotate gear 610. The indicia 614 are calibrated to the position of rack360 relative to handpiece 102. An alignment mark 573 (FIG. 21) can beplaced on tube 566. The depth gauge 600 is read from the indicia 614where indicia 614 align with alignment mark 573. Depth gauge 600 iscalibrated to correspond to the position of rack 360 and provide anumerical readout of a distance that rack 360 is extended from orinserted into tube 566 which corresponds to a measure of the length ofthe drill bit 180 that is inserted into a bone bore.

The remaining components of rotary surgical drill 500 includingcontroller 450 and the electrical connections shown in the electricalschematic (FIG. 13) are the same as previously described for rotarysurgical drill 100. Controller 450 controls the operation of brakingmechanism 520.

B. Operation

The operation of rotary surgical drill 500 is substantially similar aspreviously described in FIGS. 14A-14C for the operation of rotarysurgical drill 100. When drill bit 180 is drilling into bone 490, asshown in FIGS. 14A and 14B, rotary surgical drill 500 operates in thesame manner as rotary surgical drill 100.

With reference to FIGS. 13, 14C, 17 and 20, eventually, the drill bittip 183 cuts through the distal side 494 of bone 490 in which the bore498 is being formed. When the drill bit cuts through the distal side 494of bone 490, the frictional force created by the drill bit 180 rubbingagainst the bone 490 rapidly decreases. The current drawn by motor 122will rapidly increases. The speed of drill bit 180 also increases. Thesudden drop in the current drawn by the motor over a time period ismeasured or sensed by sensor 464 and transmitted as an electrical signalto controller 450. In one embodiment, the change in current or currentdrop over a time period can have units of milliamps per second.Processor 452, which is executing braking module software 470, comparesthe received change in current data from sensor 464 to a pre-determinedthreshold change in current or current drop level stored in sensorparameter threshold values 472.

In response to the received change in current being greater than thethreshold change in current level, processor 452 triggers the engagementof braking mechanism 520 by turning on solenoid 252. When solenoid 252is turned on, the magnetic field generated by solenoid 252 attracts thesteel flange 288 and overcomes the spring force of coil spring 350.Flange 288 and the attached plunger 280 move upwardly until flange 288contacts with the surface 254 of solenoid 252. At the same time, theupward movement of plunger 280 forces gear tooth 304 into engagementwith gear teeth 374 of rack 360, locking rack 360 to handpiece 102. Whengear tooth 304 is engaged with gear teeth 374, handpiece 102 isprevented from advancing distally forward towards the drill stop 420. Byextension this prevents the advancement of the drill bit 180. Thus, thelike first embodiment of the invention this embodiment of the inventionreduces the likelihood that an advancing drill bit will damage tissue497 adjacent to the distal side 494 of the bone bore.

After braking mechanism 520 has stopped advancement of the drill bit180, the length of the drill in the bone bore 498 is equal to thedistance between the distal end 430 of tissue protector sleeve 424 andthe distal tip 183 of drill bit 180. This length is the approximatelength that is required for a bone screw that is to be inserted into thebone bore. The linear measurement scale or depth gauge 370 that isaffixed to one or more sides 368 of rack 360 is calibrated to correspondto the length of the drill bit 180 that extends beyond the distal end430 of tissue protector 420. Measurement scale 370 is read by themedical practitioner through magnifying lens 512 at the intersection ofmeasurement line 514 with measurement scale 370.

The length of the drill in the bone bore 498 can also be read from depthgauge 600. Depth gauge 600 is calibrated to correspond to the length ofthe drill bit 180 that extends beyond the distal end 430 of tissueprotector 420. The depth gauge 600 is read by the medical practitionerfrom the indicia 614 (FIG. 25) where indicia 614 align with alignmentmark 573 (FIG. 21).

Depth gauges 370 and 600 allow for the correct length of bone screw tobe selected by the medical practitioner to match the depth of the bonebore. Depth gauges 370 and 600 can assist in preventing bone screws thatare too long or too short from being selected for use.

IV. Rotary Surgical Drill with End Mounted Brake Having an InternalTelescoping Mechanism

FIGS. 26-29 illustrate another embodiment of a rotary surgical drill 700that has an end mounted brake mechanism 900. Rotary surgical drill 700comprises a handpiece 102, chuck assembly 720, drill bit 180, controller450 and brake mechanism 900. Rotary surgical drill 700 shares many ofthe same components as rotary surgical drill 100 of FIG. 1. In thediscussion of rotary surgical drill 700, components that are common torotary surgical drill 100 will be referred to using the same referencenumbers. Rotary surgical drill 700 has a handpiece 102 that contains therotary electric motor 122. Handpiece 102 of FIGS. 26-29 is substantiallysimilar to the previously described handpiece 102 of FIG. 1. Chuckassembly 720 of FIGS. 26-30 is different than chuck assembly 140 of FIG.1.

A. Chuck and Drill Bit

Retainer Assemblies

As seen in FIG. 27, chuck assembly 720 comprises a release collar 722,an inner coupler 730 and an outer coupler 750. The inner coupler 730 hasa proximal end 732 affixed to planetary gear assembly 128 (FIG. 28) anda distal end 734 affixed to outer coupler 750 (FIG. 28). Externalthreads 735 are defined on the outer annular surface of the innercoupler distal end 734. A bore 736 extends entirely through the centerof inner coupler 730. Inner coupler 730 is formed from a single piece ofmetal. As the motor 122 rotates, planetary gear assembly 128 drivesinner coupler 730 causing a like rotation of outer coupler 750. Therelease collar 722 is coupled to the distal end of outer coupler 750.

Referring to FIGS. 30 and 31, details of the outer coupler 750 areshown. The outer coupler 750 is formed from a single piece of metal.Outer coupler 750 is generally cylindrical in shape. The outer coupler750 has a proximal end 752 and a distal end 754. Outer coupler 750 hastwo adjacent cylindrical sections, a base section 756 and a head section758. The head section 758 has a diameter that is less than the diameterof base section 756.

Base section 756 has an outer annular surface 757 and a bore 759 that isdefined by an inner annular surface 760. The bore 759 terminates atterminal wall 761. Internal threads 762 are formed on the proximalportion of inner annular surface 760. The inner coupler distal end 734is seated in bore 759 and affixed to outer coupler 750 by the mating ofinner coupler external threads 735 with the outer coupler internalthreads 762.

The head section 758 has an outer annular surface 764 and a pair ofcoaxial bores 766 and 767. The distal most bore 766 is round and theproximal bore 767 is square. Bore 767 is defined by four opposedorthogonal surfaces 768. The head section 758 further includes an angledface 770 that extends from annular surface 764 and terminates in adistally oriented face 772 at distal end 754. An annular step 774 isdefined at the junction of head section 758 and base section 756.

A pair of opposed angled arcuate slots 778 are formed on opposite sidesof head section 758. Slots 778 are defined by opposed angled slot walls780. The slots 778 begin at the outer surface 764 of head section 758,above step 774 and are angled in a distal direction inwardly toward bore766. At the base of slot 778, an oval shaped hole 780 is defined thatextends from slot 778 into bore 766.

Four spaced apart bores 784 are defined through head section 758. Bores784 are defined by inner annular surfaces 786. The bores 784 areparallel in length to bores 766 and 768. Each of the bores 784 extendbetween the distal face 772 and the terminal wall 761 at the end of bore759.

Returning to FIGS. 27 and 28 and with continued reference to FIGS. 30and 31, a drill bit retainer assembly 800 is illustrated. The drill bitretainer assembly 800 includes outer coupler 750, release collar 722,coil spring 802, ring 804 and a pair of elongated rods or pins 810.Release collar 722 is generally cylindrical in shape and is formed froma single piece of metal. The release collar 722 has a thru bore 723defined by an inner annular surface 724.

The drill bit retainer assembly 800 is assembled with coil spring 802mounted over outer coupler outer annular surface 764 and the coil springproximal end resting in contact with annular step 774. Ring 804 isplaced over outer annular surface 764 and moved into contact with thecoil spring distal end. The outer coupler head section 758 extendsthrough ring hole 805. Ring 804 is moved in a proximal directioncompressing spring 802 and allowing pins 810 to be inserted into outercoupler slots 778. The release of ring 804 causes coil spring 802 tobias ring 804 and pins 810 to the distal ends of slots 778 adjacentholes 780. In this position, the center of pins 810 at least partiallyextend through holes 780 into outer coupler bore 766.

The release collar 722 is placed over ring 804 and spring 802 such thatthe collar inner annular surface 724 is adjacent the spring 802 and thedistal end of spring 802 rests in contact with the proximal directedsurface of ring 804. The distal directed surface of ring 804 is incontact with an annular lip within release collar 722. A set screw andslot (not shown) allow release collar 722 to be movably retained toouter coupler 750.

The drill bit 180 is inserted into chuck assembly 720 by a user graspingrelease collar 722 and moving release collar 722 in a proximal directionsuch that pins 840 move away from the center axis of output coupler 750and spring 802 is compressed. The drill bit square drive head 182 isinserted into bore 766 and moved in a proximal direction until seated inthe complimentary square shaped outer coupler bore 768 (FIG. 31).

When the release collar 722 is released by the user, the spring 802biases the release collar 722, ring 804 and pins 810 to move in a distaldirection such that pins 810 move from slots 778 through holes 780 andinto engagement with the complementary grooves 187 in drive head 182.With pins 810 disposed in grooves 187, the drill bit 180 is held andretained to output coupler 750. Drill bit 180 is removed from chuckassembly 720 by manually depressing release collar 722 towards case 103.This results in a like removal of pins 810 from the complementarygrooves 187 allowing removal of drill bit 180 from drill bit retainerassembly 800.

B. Brake Mechanism

Brake mechanism 900 comprises a linear actuator 250 mounted in anactuator housing 1020 and a telescoping protector assembly 910.Telescoping protector assembly 910 is described with reference to FIG.32. Telescoping protector assembly 910 includes an elongated stop 920,four elongated bars 940, tissue protector 950, spring cover 990 and rodor rack 980. Rack 980 is mounted for sliding movement within previouslydescribed tube 129 (FIG. 36). With specific reference to FIG. 34, stop920 includes an elongated rod 922 with an attached head 928. Stop 920has a proximal end 924, distal end 926 and a disk shaped head 928. Head928 is perpendicular to rod 922 and extends over distal end 926. Head928 further has a proximal face 930 and a distal face 932. Threadedapertures 934 are defined in head 928 and extend between the proximalface 930 and the distal face 932.

Turning to FIGS. 35A and 35B, tissue protector 950 is shown. The tissueprotector 950 has a tube shaped base 952. A sleeve 960 is disposed inand projects distally out of base 952. A bearing assembly 951, seen inFIG. 27, is disposed between the inner wall of the base 952 and theouter surface of the sleeve that rotatably holds the sleeve 960 to base952. Base 952 has an outer circumferential surface 954, a proximal face956 and a distal face 958. Sleeve 960 extends in a distal direction awayfrom a wall 962 at the bottom of an annular slot 964 defined in distalface 958. A hole 966 extends entirely thru the base 952 and sleeve 960.Hole 966 is defined in sleeve 960 by an inner annular surface 968.Sleeve 960 terminates in a distal end 970. Four equally spaced apartapertures 972 are formed in base 952. Apertures 972 extend betweenproximal face 956 and distal face 958.

Referring to FIG. 33, each of the four elongated bars 940 have athreaded proximal end 942 and a distal end 944. Threaded proximal ends942 are screwed into the threaded apertures 934 of stop head 928. Thedistal ends 942 are mounted thru apertures 972 (FIG. 35B) in base 952.The distal ends 972 are retained to base 952 by suitable means such aswelding or swaging. The stop 920, bars 940 and tissue protector 950 canbe formed from suitable materials such as metal.

Rack 980 is shown in FIGS. 37A and 37B. Rack 980 has an elongated shapewith a round cross-sectional profile. Rack 980 can be formed fromsuitable materials such as metal. Rack 980 has a center section 981, aproximal end 982 and a distal end 983. A recess 984 is defined in theupper side of rack 980 between the center section 981 and the proximalend 982. Recess 984 terminates at opposed end walls 985. A set of gearteeth 986 are formed in the lower side of rack 980 between the centersection 981 and the proximal end 982. Teeth 986 are dimensioned suchthat tooth 304 (FIG. 8B) can be engaged between two teeth 986. A flange987 encircles rack 980 toward the center section 981.

Turning to FIG. 38, the spring cover 990 has a truncated cylindricalshaped with one flat side 996. Spring cover 990 has an outercircumferential surface 995, a proximal face 992 and a distal face 994.A bore 997 extends thru spring cover 990. A counter-bore 998 extendsfrom distal face 994 in a proximal direction terminating at end wall1000. A rectangular shaped opening 1002 is defined at the bottom of wall1000. A threaded aperture 1004 extends from the top of outer surface 995downwardly and ends at bore 997. Threaded aperture 1004 is dimensionedto receive a set screw 1006 (FIG. 37A).

With continued reference to FIG. 37A, rack sub-assembly 1007 is shown. Acoil spring 1008 is mounted over the proximal end 982 of rack 980. Coilspring 1008 has a proximal end 1009 and a distal end 1010. Distal end1010 abuts flange 987. The coil spring 1008 surrounds the recess 984.The spring cover 990 slides over the proximal end 982 of rack 980. Theproximal end 982 extends thru bore 997. The spring cover 990 ispositioned toward the proximal end of recess 984 and is coupled to rack980 for sliding movement by set screw 1006. Rack 980 can slide inproximal and distal directions relative to spring cover 990. The setscrew 1006 is screwed into threaded aperture 1004 until the terminal endof set screw 1006 extends slightly into recess 984 between the recessend walls 985. The proximal end 1009 of the coil spring abuts the endwall 1000 of spring cover 990.

The rack sub-assembly 1007 of FIG. 37A is inserted into tube 129.Referring to FIGS. 29, 32 and 36, the distal end 983 of rack 980 isinserted into the proximal opening 974 of the motor shaft and into lumen976. Rack 980 and coil spring 1008 move into tube 129 until flange 987abuts the interior wall of tapered section 977. In this position, thedistal end 983 of the rack is located in opening 975. Rack 980 can slidewithin lumen 976. The travel of rack 980 in the distal direction islimited by the abutment of set screw 1006 against the proximal wall 985in recess 984. The travel of rack 980 in the proximal direction islimited by the compression of spring 1008 and the abutment of set screw1006 against the distal wall 985 in recess 984. Spring 1008 biases rack980 in a distal direction relative to motor shaft 130.

Referring to FIGS. 28, 31 and 32, the stop 920 is illustrated as beingmounted within outer coupler 750. Stop 920 is inserted into bore 760such that the distal face 932 of head 928 abuts terminal wall 761 withthe four bars 940 extending thru the four bores 784 of outer coupler 750and away from outer coupler distal face 772. The tissue protector 950 ismounted to the distal ends of the four bars 940. The outer coupler 750is inserted into shroud 111 and attached to inner coupler 730 by themating of the outer coupler internal threads 762 with the inner couplerexternal threads 735 (FIG. 27). The proximal end 924 of the stop extendsthrough the center bore 736 of inner coupler 730 and abuts against thedistal end 983 of rack 982. Stop rod 922 slides within bore 736.

Another coil spring 1012 is mounted in bore 760 surrounding the distalportion of rod 922. Coil spring 1012 has a distal end 1013 that abutsthe proximal face 930 of stop head 928. Coil spring 1012 further has aproximal end 1014 that abuts the base of the bore 736 within innercoupler 730. The coil spring 1012 biases stop 920 is a distal directionaway from inner coupler 730. Stop 920 can travel between an extendedposition where head 728 abuts the terminal wall 761 of the outer couplerand a retracted position where spring 1012 is compressed.

The drill bit 180 is inserted through tissue protector 950.Specifically, the square drive head 182 is inserted through bore 966 andthrough the space between bars 940 and is received by drill bit retainerassembly 800. When drill bit 180 is seated and held in drill bitretainer 800, the drill bit head 182 abuts the distal face 932 of stop920.

The brake mechanism 900 further comprises a linear actuator 250 mountedin an actuator housing 1020. Referring to FIGS. 39 and 40, the actuatorhousing 1020 is mounted to the proximal end 107 of case or upper housing103. Actuator housing 1020 has holes 1022 and case 103 has threadedapertures 1024. Specifically, the actuator housing 1020 is mounted toupper housing 103 adjacent to proximal end 107 by screws 1026 extendingthru holes 1022 and received in threaded apertures 1024.

The actuator housing 1020 is formed from suitable materials such asmachined metal. Actuator housing 1020 is generally rectangular with aD-shaped cross-section. The housing 1024 has a proximal end 1028 and adistal end 1030.

Housing 1024 is defined by a U-shaped upper wall 1032 that is attachedto a planar lower wall 1034 and an end wall 1036 that covers theproximal end 1028. Housing 1024 has an outer surface 1038 and an innersurface 1040. Walls 1032, 1034 and 1036 define an interior actuatorcavity 1042 that opens in a proximal direction. The end wall 1036 hastwo apertures, a center aperture 1044 and another aperture 1046 that islocated between aperture 1044 and upper wall 1032. The proximal end 982of rack 980 can move through center aperture 1044 when rack 980 ismoved.

A pair of diametrically opposed rectangular shaped support members 1048extend into cavity 1042 from opposite sides of U-shaped upper wall 1032.Each support member 1048 has a planar top surface 1050 and an inwardlyextending lower lip 1051. A rectangular shaped block 1052 is formed onthe interior facing surface of lower wall 1034 and extends upwardly intocavity 1042. A bore 1054 extends entirely thru block 1052 and lower wall1034. A counter-bore 1049 (FIG. 29) extends from the outer surface oflower wall 1034 into block 1052. Counter-bore 1049 terminates at an endwall 1051 (FIG. 29).

A plate 1056 has ends 1055 that rest on top surface 1050 of supportmembers 1048. Plate 1056 is attached to support members 1048 by the useof fasteners or adhesives. Plate 1056 has an upper surface 1057, lowersurface 1058 and a distal facing opening 1059. A pair of apertures 1060are defined thru plate 1056 on opposite sides of opening 1059.

The linear actuator 250 is mounted within actuator housing cavity 1042.Solenoid 252 is mounted in cavity 1042 between support members 1048 withthe solenoid top surface 254 supported by lower lip 1051. The solenoidpins 266 extend into and are retained in plate apertures 1060. In oneembodiment, apertures 1060 and pins 266 are dimensioned such that pins266 are press fit into apertures 1060.

The plunger 280 is mounted in solenoid 252. Plunger hub 282 is mountedin solenoid bore 260. The D-shaped terminal section 298 of plunger 280extends through solenoid bore 264 (FIG. 7B) with gear tooth 304extending slightly beyond lower surface 256 and into plate opening 1059.

The plunger flange 288 extends over the surface 254 of solenoid 252. Theplunger post 290 extends downwardly through the block bore 1054 andterminates at end 292 which is positioned slightly beyond the lower wall1034. A coil spring 350 is mounted in counter-bore 1049 and surroundsplunger post 290. A nut 352 is threaded onto the threads 294 (FIG. 8B)of post 290. Coil spring 350 is compressed between nut 352 and end wall1051. Coil spring 350 biases plunger 280 in a downward direction awayfrom solenoid 252.

A flexible cable 274 extends from solenoid 252 and is routed into case103. Cable end 275 is connected to terminals 268 of solenoid 252. Cableend 276 is electrically connected to terminals (not shown) located inhandpiece upper housing 103 which connect with PCB 118 (FIG. 28).

A space or gap 354 is defined between the top side of block 1052 and thebottom surface of plunger flange 288. Plunger flange 288 can move in gap354 between a first position when solenoid 252 is de-energized or turnedoff and coil spring 350 biases flange 288 into contact with the top sideof block 1052. When solenoid 252 is energized or turned on, the magneticfield generated by solenoid 252 attracts the steel flange 288 andovercomes the spring force of coil spring 350, thereby moving flange 288into contact with the bottom surface 254 of solenoid 252.

The remaining components of rotary surgical drill 700 includingcontroller 450 and the electrical connections shown in the electricalschematic (FIG. 13) are the same as previously described for rotarysurgical drill 100. Controller 450 controls the operation of brakingmechanism 900.

C. Operation

As shown in FIG. 41A, the rotary surgical drill 700 is used at asurgical site 488. The medical practitioner grasps handle 104 anddirects the drill bit tip 183 to the surgical site. Drill bit 180 isused to drill one or more bores into a bone.

With further reference to FIGS. 13, 28 and 29, initially, the solenoid252 is turned off by controller 450 such that spring 350 biases plunger280 to a lower most position where tooth 304 is disengaged from theteeth 986 of rack 980. In this position, rack 980 is free to telescopeor slide within lumen 976. Stop 920 likewise free to slide within outercoupler bore 760 and inner coupler bore 736.

Because tissue protector 950 is coupled to rods 940 which are coupled tostop 920, which is coupled to rack 980, displacement of tissue protector950 relative to drill bit 180 causes a like displacement of rack 980.Initially, the tissue protector 950 is biased by coil springs 1012 and1008 to a distal most position where distal end 970 is slightly drawnback from drill bit distal tip 183 causing only the distal tip 183 to beexposed as seen in FIG. 41A. In this position, the stop 920 abuts theouter coupler terminal wall 761. Also initially, the drill bit 180 isnot subjected to any axial loading.

The drill bit 180 is positioned against the proximal side 492 of thebone 490 where the bone bore 498 is to be formed. The drill bit 180 isforced downwardly in an axial direction. After the drill bit 180 is sopositioned, the rotary drill 700 is actuated in a forward or clockwiserotation. The combination of the rotating drill bit and the axial loadplaced on the drill bit results in the cutting edges of the drill bittip 183 cutting the bone 490 so as to form a bore 498. During formationof the bone bore, the motor 122 draws a relatively high current tomaintain a desired number of revolutions per minute (RPM) of the drillbit 180. The current level drawn by motor 122 is measured by sensor 464and transmitted as an electrical signal to controller 450.

Referring to FIG. 41B, as the drill bit tip 183 enters the bone, thedistal end 970 of the tissue protector abuts against the proximal side492 of bone 490 limiting the forward movement of tissue protector 950.As the drill bit 180 continues to rotate, the combination of therotating drill bit and the axial load placed on the drill bit by themedical practitioner overcomes the spring force of coil springs 1012 and1008 and the interference fit between the inner surface of sleeve 960and the outer circumference 186 of the drill bit. Handpiece 102 istherefore able to advance towards the tissue protection 950. As the bonebore 498 is formed, the length of the drill bit 180 exposed or extendingbeyond the distal end 970 of the tissue protector increases. Continuedrotation of the drill bit and axial loading causes the drill bit tip 183to penetrate through the bone and bone marrow 496 and to approach thedistal side 494 of bone 490.

At the same time the drill bit 180 is advancing, the outer coupler 750,the inner coupler 730, the hollow motor shaft 130 and the rest of therotary surgical drill 700 advance with the drill bit. The outer couplerslides over the static rods 940. Stop 920 thus appears to retract intoouter coupler bore 760 and inner coupler bore 736. The abutment ofplunger proximal end 924 against rack distal end 983 causes rack 980 toapparently slide within motor shaft lumen 976. (It should be understoodthat rack is static and the handpiece advances over the rack.) Thesliding movement of outer coupler 750 relative to stop 920 causescompression of coil spring 1012. The sliding movement of motor shaft 130relative to rack 980 causes compression of coil spring 1008. As thehandpiece 102 advances, the proximal end 982 of the rack extends throughaperture 1044 outwardly away from actuator housing 1024.

With reference to FIG. 41C, eventually, the drill bit tip 183 cutsthrough the distal side 494 of bone 490 in which the bone bore 498 isbeing formed. For the reasons set forth above with respect to theearlier described versions of the invention, sensor 464 detects theoccurrence of this event as a change in motor current draw. Processor452, which is executing braking module software 470, compares thereceived change in current data from sensor 464 to a pre-determinedthreshold change in current or current drop level stored in sensorparameter threshold values 472.

In response to the received change in current being greater than thethreshold change in current level, processor 452 triggers the engagementof braking mechanism 900 by turning on solenoid 252. When solenoid 252is turned on, the magnetic field generated by solenoid 252 attracts thesteel flange 288 (FIG. 39) and overcomes the spring force of coil spring350, thereby moving flange 288 and the attached plunger 280 upwardlyuntil flange 288 contacts with the surface 254 of solenoid 252. At thesame time, the movement of plunger 280 forces gear tooth 304 intoengagement with gear teeth 986 (FIG. 29) of rack 980, locking rack 980to handpiece 102. When gear tooth 304 is engaged with gear teeth 980,handpiece 102 is prevented from further advancement relative to rack980. By extension, drill bit 180 is likewise prevented from furtheradvancement. This substantially reduces the unintended cutting of tissue497 adjacent to the distal side 494 of the bone bore 498 by the drillbit.

After the braking mechanism 900 has stopped advancement of the drill bit180, the length of the drill in the bone bore 498 is equal to thedistance between the distal end 970 of the tissue protector and thedistal tip 183 of drill bit 180. This length is the approximate lengththat is required for a bone screw that is to be inserted into the bonebore.

The medical practitioner will pull the drill bit 180 out from the bonebore 498. If the bone bore is deep, the fit between the drill bit andthe bone bore can be a particularly tight fit. The medical practitionercan rotate drill bit 180 in a reverse (counterclockwise) direction usingreverse trigger switch 117 to disengage drill bit 180 from the bonebore. With the drill bit 180 removed from the bone bore, the medicalpractitioner can complete the procedure for which the bore was formed.

Before the medical practitioner uses rotary surgical drill 700 to formanother bore, braking mechanism 900 is disengaged. In one embodiment,processor 452 turns off solenoid 252 after sensing the depression ofreverse trigger switch 117. In another embodiment, processor 452 turnsoff solenoid 252 after detecting a certain sequence of depression of thetrigger switches 116, 117. For example, processor 452 can turn offsolenoid 252 after detecting the simultaneous depression of both triggerswitches 116 and 117. In an additional embodiment, a separate switch(not shown) can be provided to turn off solenoid 252. After solenoid 252is turned off, spring 350 biases plunger 280 to move in a downwarddirection causing disengagement of gear tooth 304 from teeth 986. Rack980 is now free to slide within lumen 976.

With rack 980 free to move, the compressed coil spring 1008 causes rack980 to slide in a distal direction within motor shaft 130. At the sametime, the compressed coil spring 1012 causes the stop 920 to slide in adistal direction within outer coupler bore 760 forcing tissue protector950 to be extended over drill bit 180.

V. Rotary Surgical Drill with Telescoping Member that Retracts with theActuation of the Drill Bit

FIGS. 42-46 illustrate an additional embodiment of a rotary surgicaldrill 1100 that has a brake mechanism 1150. Rotary surgical drill 1100comprises handpiece 102, brake mechanism 1150, chuck assembly 1200,drill bit 1500, controller 450 and retracting sleeve mechanism 1600. Inparticular, brake mechanism 1150 comprises chuck assembly 1200, drillbit 1500 and retracting sleeve mechanism 1600. The rotary surgical drill1100 has the same handpiece 102 and controller 450 as rotary surgicaldrill 100 of FIG. 1. In the discussion of rotary surgical drill 1100,components that are common to rotary surgical drill 100 will be referredto using the same reference numbers.

A. Chuck Assembly

With reference to FIGS. 42, 47 and 51, chuck assembly 1200 is shownmounted to handpiece 102. Chuck assembly 1200 is removably attachable tohandpiece 102. The chuck assembly 1200 includes an end cap 1210 that iscylindrical in shape and has a proximal end 1212 and a distal end 1214.A flange 1215 extends circumferentially around distal end 1214. Externalthreads 1216 are defined in the outer annular surface of flange 1215.End cap 1210 is formed from a single piece of metal. The end cap 1210 ismounted within the bore 1618 of connecting hub 1610 (FIG. 47) by themating of external threads 1216 with internal threads 1620 in hub 1610.

End cap 1210 has an outer annular surface 1217. A bore 1218 extendsthrough end cap 1210 and defines an inner annular surface 1220. A pairof diametrically opposed slots 1221 are defined thru opposite sides ofend cap 1210 slightly spaced from the proximal wall of flange 1215. Anarcuate V-shaped cutout 1224 is located in end cap 1210 and extends fromproximal end 1212 towards distal end 1214 and terminates in an arcuateslot 1226. Cutout 1224 is contiguous with slot 1226.

Handpiece 102 has a pin (not shown) that extends downwardly from the topof case 103 into handpiece opening 112. Chuck assembly 1200 is attachedto handpiece 102 (FIG. 42) by inserting the end cap proximal end 1212into handpiece opening 112 with the pin aligned with the V-shaped cutout1224. As end cap 1210 is moved in a proximal direction into opening 112,the pin will contact the base of slot 1226. End cap 1210 and the entirebrake mechanism 1150 are then rotated counter clockwise causing the pinto be captured in slot 1226. The pin and slot 1226 are dimensioned suchthat the pin and slot 1226 form a snug interference fit. The end cap1210 and brake mechanism 1150 are now affixed to handpiece 102.

Chuck assembly 1200 includes an input drive shaft 1240. Input driveshaft 1240 is illustrated with reference to FIGS. 47, 48 and 51. Inputdrive shaft 1240 is formed from a single piece of metal. Input driveshaft 1240 is generally cylindrical in shape. The input drive shaft 1240has a center section 1241, a proximal end 1242 and a distal end 1244.Input drive shaft 1240 includes a head 1246 located at distal end 1244.Shaft head 1246 is formed with radially outwardly extending gear teeth1248. Input drive shaft 1240 also has an outer surface 1250 and aproximal bore 1252 (FIG. 51) that extends thru the proximal end of inputdrive shaft 1240. The proximal bore 1252 is D-shaped such that one side1253 (FIG. 51) of the inner surface of bore 1252 is flat. A counter bore1254 is defined in head 1246 and extends from distal end 1244 in aproximal direction terminating at step 1255. Counter bore 1254 definesan inner surface 1255. Bore 1252 and counter bore 1254 are co-axial andcontiguous.

Two annular grooves 1256 and 1257 are defined in outer surface 1250 andwithin center section 1251. Another annular groove 1258 is defined inouter surface 1250 slightly spaced from proximal end 1242. A pair offlat faces 1260 is defined on opposite sides of outer surface 1250. Flatfaces 1260 extend from groove 1258 to slightly beyond a hole 1262. Hole1262 extends perpendicularly thru one of the flat faces 1260 into bore1252. A tapered conical seat 1264 surrounds hole 1262 and facesoutwardly.

Bearings 1270 and 1272, both identified in FIG. 51, are press fit intothe distal end of the end cap bore 1218. Bearings 1270 and 1272 areseated in bore 1218 with the outer surface of the bearings surrounded byinner annular surface 1212. Bearings 1270 and 1272 each have a centralaperture that the drive shaft 1240 is extends through. Bearings 1270 and1272 support drive shaft 1240 for rotary motion within end cap 1210 andhub 1610. Bearings 1270 and 1272 are retained between the proximal faceof head 1246 and a retaining ring 1274 that is affixed in groove 1256.

Turning specifically to FIG. 47, the chuck assembly 1200 includes adrill bit retainer assembly 1275. Drill bit retainer assembly 1275includes an outer release collar 1280, an inner release collar 1300 anda pin holder 1330. The outer release collar 1280 is generallycylindrical in shape and has a proximal face 1282, a distal face 1284and a central passage 1286. An annular circumferential lip 1288surrounds the distal face 1284. A pair of diametrically opposed throughholes 1290 are defined thru outer release collar 1280 slightly spacedfrom lip 1288.

With additional reference to FIG. 49, details of the inner releasecollar 1300 is now described. The inner release collar 1300 is generallycylindrical in shape and has a proximal end 1302, a distal end 1304, anouter annular surface 1305 and a central passage 1306. A distal facingrecess 1308 (FIG. 51) is defined in distal end 1304. The distal facingrecess 1308 terminates at the distal face of a wall 1310. A pair ofdiametrically opposed internally threaded apertures 1312 are definedthru inner release collar 1300 between distal end wall 1304 and wall1310. A proximal facing recess 1314 is defined in proximal end 1302. Theproximal facing recess 1314 terminates at the proximal face of wall1310. Recess 1314 is defined by an annular ramp 1316 that extendsdistally forward from the proximal end of collar 1300 1314. Extendingdistally, ramp angles inwardly toward dividing wall 1310 terminating atdetent 1318.

Referring to FIGS. 50 and 51, pin holder 1330 is shown. The pin holder1330 is generally cylindrical in shape and has a proximal face 1332, adistal face 1334, an outer circumferential surface 1335 and a centralpassage 1336. The central passage 1336 is defined by a pair ofdiametrically opposed arcuate walls 1338 and by a pair of diametricallyopposed flat walls 1340 that all face into passage 1336. A bore 1342 isdefined thru pin holder 1330 between outer surface 1335 and one of theflat walls 1340. Bore 1342 has an interior opening 1343 adjacent flatwall 1340 and an exterior opening 1344 adjacent outer surface 1335. Anannular shoulder 1346 is defined within bore 1342.

A pin 1350 and coil spring 1360 are mounted in pin holder 1330.Specifically, pin 1350 is cylindrical in shape with a rounded inner end1352 and a rounded outer end 1354. An annular flange 1356 (FIG. 47)surrounds the central portion of pin 1350. The coil spring 1360 ismounted around the inner end 1352 of pin 1350. Coil spring 1360 has ends1361 and 1362.

Pin 1350 is mounted in bore 1342 with the outer end 1354 extendingthrough exterior opening 1344 and the inner end 1352 extending throughinterior opening 1343. Coil spring 1360 is positioned in bore 1343 withend 1361 seated against the conical seat 1264 of input drive shaft 1240and end 1362 seated against flange 1356. Coil spring 1360 biases pin1350 away from input drive shaft 1240.

Pin holder 1330 is received in the proximal facing inner release collarrecess 1314 with the distal face 1334 abutting the proximal face ofdividing wall 1310. The pin holder passage 1336 is mounted over driveshaft 1240. Pin holder 1330 is slid over drive shaft proximal end 1242such that the drive shaft flat faces 1260 are juxtaposed to the pinholder flat walls 1340. Pin holder 1330 is retained in recess 1314 andheld to input drive shaft 1240 by a retaining ring 1364. Ring 1364 isseated in drive shaft groove 1257.

With reference to FIGS. 47 and 51, the inner release collar 1300 isdisposed for sliding movement within bore 1218 of end cap 1210. Outerrelease collar 1280 is disposed for sliding movement around the outersurface 1217 of end cap 1210. A coil spring 1366 is mounted over driveshaft 1240 around center section 1241. Coil spring 1366 has a proximalend that abuts the distal face of dividing wall 1310 and a distal endthat abuts the retaining ring 1274. Coil spring 1366 biases the innerrelease collar 1300 in a proximal direction away from bearing 1272.

The threaded screws 1368 have a head 1369 that abuts the outer surfaceof outer release collar 1280. Screws 1368 extend through holes 1290,through slots 1221 of end cap 1210 and are received in threadedapertures 1312 of inner release collar 1300. Screws 1368 connect theouter release collar 1280 to the inner release collar 1300 such thatmovement of outer release collar 1280 results in a like movement ofinner release collar 1300. The combination of the outer 1280 and inner1300 release collars can slide longitudinally in end cap 1210. Themovement of outer 1280 and inner 1300 release collars is limited by theabutment of screws 1369 with the ends of slots 1221. The outer 1280 andinner 1300 release collars are biased in a proximal direction by coilspring 1366 such that screws 1369 normally abut the proximal ends ofslots 1221. In this static position, the outer end 1354 of pin 1350abuts against and slightly into detent 1318.

Turning to FIG. 52, the drill bit 1500 is shown. Drill bit 1500 has anelongated rod shape with a center shaft or section 1510, a proximal end1512 and a distal pointed cutting tip 1514. A drive head 1520 is definedat proximal end 1512. Drive head 1520 has a D-shaped cross-section withan arcuate surface 1521 and a flat surface 1522. Flat surface 1522extends from the proximal end 1512 in a distal direction and terminatesat a step 1524. An annular raised portion 1530 is spaced from step 1524.A pair of diametrically opposed grooves 1526 are defined in the arcuatesurfaces 1521.

The drill bit 1500 is retained in chuck assembly 1200 by drill bitretainer assembly 1275. Referring to FIG. 51, the drive head 1520 isreceived within input drive shaft D-shaped bore 1252 and bore 1254. Thedrill bit 1500 can move in a proximal direction relative to input driveshaft 1240 until drill bit step 1524 abuts the input drive shaft step1255. The flat surface 1522 abuts a flat interior surface within bore1252. As the drill bit 1500 seats into D-shaped bore 1252, coil spring1360 biases pin end 1352 to move through hole 1262 and into engagementwith groove 1526. In this position, the drill bit 1500 is clamped withinchuck assembly 1200 by pin 1350.

Drill bit 1500 is removed from chuck assembly 1200 by releasing drillbit retainer assembly 1275. A medical practitioner grasps the outerrelease collar 1280 and moves the outer release collar in a distaldirection causing compression of coil spring 1366. The movement of theouter release collar 1280 in the distal direction is limited by theabutment of screws 1369 with the distal end of slots 1221. Distalmovement of the outer release collar 1280 causes a like movement of theinner release collar. More particularly the inner release collar isdisplaced so that the portion of the collar that defines detent 1318moves forward of pin 1350. Spring 1360 forces pin 1350 outwardly frombore 1342 and pin outer end 1354 tracks or slides along ramp 1316. Asthe pin outer end 1354 reaches the proximal end of ramp 1316, the innerend 1352 of the pin withdraws from drill bit groove 1526. This allowsthe drill bit 1500 to be removed from inner drive shaft 1240 and chuckassembly 1200.

Referring to FIGS. 47 and 51, driving collar 1400 is now described. Thedriving collar 1400 is generally cylindrical in shape and has a proximalface 1402 and a distal face 1404. Driving collar 1400 has an outerannular surface 1406 and a bore 1408 with two flat sides and two arcuatesides. A cutout 1410 is located in proximal face 1402 and extends fromthe outer annular surface 1406 to the center of bore 1408 and fromproximal face 1402 approximately half the length of collar 1400.

Driving collar 1400 is mounted over input drive shaft proximal end 1242such that the input drive shaft extends through bore 1408. The inputdrive shaft flat sides 1260 (FIG. 48) are adjacent the flat sides ofbore 1408 and the input drive shaft arcuate sections are adjacent thearcuate sides of bore 1408.

A retaining ring 1420 is affixed in input drive shaft groove 1258. Theretaining ring 1420 holds the driving collar 1400 on input drive shaft1240. A coil spring 1424 is mounted over input drive shaft 1240 betweenretaining ring 1364 and the distal face 1404 of driving collar 1400.Spring 1424 biases driving collar 1400 in a proximal direction away frompin holder 1330. When chuck assembly 1200 is attached to handpiece 102,the driving collar 1400 engages motor shaft 130 (FIG. 3) such that therotation of the motor shaft 130 rotates driving collar 1400 causing alike rotation of input drive shaft 1240 and drill bit 1500.

B. Retracting Sleeve Mechanism

With reference to FIGS. 42, 48 and 51, the retracting sleeve mechanism1600 will now be described and illustrated. Retracting sleeve mechanism1600 is coupled to chuck assembly 1200. The retracting sleeve mechanism1600 comprises a connecting hub 1610, a planetary gear assembly 1700, anoutput drive shaft 1800, a ball nut 1850, a coupler 1900, a tissueprotector sleeve 2000, a first release mechanism 1750 and a secondrelease mechanism 2100.

Referring to FIGS. 53A and 53B, connecting hub 1610 is illustrated. Theconnecting hub 1610 is generally cylindrical in shape and can be formedfrom a single piece of metal. Connecting hub 1610 has a distal end 1612and a proximal end 1614. Connecting hub 1610 further has a base section1622, a center section 1624 and an end section 1626. Center section 1624has a smaller diameter than base section 1622 and end section 1626 has asmaller diameter than center section 1624. An inner annular surface 1619is located within base section 1622 and center section 1624. Innerannular surface 1619 defines a bore 1618. Internal threads 1620 aredefined on the annular surface 1619 of base section 1622. End cap 1210(FIG. 47) is attached to connecting hub 1610 by the mating of externalthreads 1216 (FIG. 47) with the internal threads 1620 in hub 1610. Basesection 1622 also has an aperture 1628 that extends perpendicularlythrough base section 1622 into bore 1618. A distal facing step 1629 isdefined at the intersection of center section 1624 with base section1622. Another distal facing step 1630 is defined at the intersection ofend section 1626 with center section 1624.

Center section 1624 has an outer annular surface 1632. Eight equallyspaced holes 1634 are formed through center section 1624 extending fromouter surface 1632 into bore 1618. An inner annular surface 1638 islocated within end section 1626 and defines a bore 1640. Bore 1640 iscoaxial and contiguous with bore 1618. An annular lip 1642 protrudesfrom distal end 1614 into bore 1640. A proximal facing step 1644 isdefined in center section 1624 at the terminal end of bore 1618.

Turning to FIG. 54, a release ring 1650 is shown. The release ring 1650has an annular shape with a proximal end 1651, a distal end 1652, anouter surface 1654 and an inner surface 1656. An opening 1658 thrurelease ring 1650 is defined by inner surface 1656. An upper threadedaperture 1660 and a diametrically opposed lower threaded aperture 1662extend perpendicularly thru opposite sides of release ring 1650. Releasering 1650 can be formed from a single piece of metal.

With additional reference to FIGS. 53A and 53B, the release ring 1650 ismounted over center section 1624 of connecting hub 1610 with the ringinterior surface 1656 surrounding the hub outer surface 1632. A setscrew 1664 is mounted through threaded aperture 1662 and is tightenedinto engagement with outer surface 1632 in order to retain release ring1650 to connecting hub 1610.

The housing 1680 is illustrated with reference to FIGS. 43 and 46.Housing 1680 is generally cylindrical in shape and can be formed from asingle piece of metal. Housing 1680 includes a distal end 1682 and aproximal end 1684. Housing 1680 has an inner annular surface 1684 thatdefines a through bore 1686. The end section 1626 of connecting hub 1610(FIG. 53A) is press fit into the proximal end of bore 1686 such that theproximal end 1682 of the housing abuts distal facing step 1630. End cap1210, connecting hub 1610 and housing 1680 are all connected together toform a unitary piece.

From FIG. 55 it can be seen that retracting sleeve mechanism 1600includes a planetary gear assembly 1700. Planetary gear assembly 1700 ismounted within bore 1618 of connecting hub 1610. The planetary gearassembly 1700 is a two stage planetary gear assembly that includes afirst stage 1710 and a second stage 1720. The first stage 1710 has threeplanet gears 1712. Planet gears 1712 engage the gear teeth 1248 of inputdrive shaft 1240. The first stage planet gears 1712 drive ring gear1730. Planet gears 1712 rotate about pins 1714 that are mounted to adisc 1716. Ring gear 1730 drives the second stage 1720 of three planetgears 1722 and a sun gear 1724 connected to disc 1716. The second stageplanet gears 1722 rotate about pins 1726 that are mounted to the head1810 of output drive shaft 1800. The second stage planet gears 1722drive output drive shaft 1800. The planetary gear assembly 1700 causes aspeed reduction in the rotational rate (RPM) of output drive shaft 1800as compared to the rotational rate of motor shaft 130.

Turning to FIG. 56, ring gear 1730 is shown. The ring gear 1730 has anannular shape with a proximal side 1732 and a distal side 1734. Acentral opening 1736 is defined thru ring gear 1730. Ring gear 1730further has an inner annular surface 1738 upon which teeth 1740 areformed and an outer annular surface 1741. Ring gear teeth 1740 engageteeth of planet gears 1712 and 1722. Eight shallow bores 1742 areequally spaced around the outer circumference of the outer annularsurface 1741. The bores 1742 extend partially into ring gear 1730 andterminate at a terminal wall 1744 within each bore. The ring gear 1730is positioned in connecting hub center section 1624 (FIG. 53B) with theouter surface 1741 adjacent and surrounded by the connecting hub innersurface 1619. Ring gear 1730 can rotate within bore 1618.

Rotary motion is transferred from input drive shaft 1240 through thefirst stage 1710 planetary gears and the second stage planetary gears todrive output drive shaft 1800. Planetary gear assembly 1700 produces aspeed reduction ratio of generally between 10 to 1 and 20 to 1. Moreoften the speed reduction is between 13 to 1 and 16 to 1.

Retracting sleeve mechanism 1600 includes a first release mechanism 1750seen in FIGS. 43 and 55. The first release mechanism 1750 is mounted torelease ring 1650. The first release mechanism 1750 includes a barrel1752 that is screwed into threaded aperture 1660 (FIG. 54). Threads (notshown) are defined on the lower exterior surface of barrel 1752. Barrel1752 has a hollow cylindrical shaped interior cavity 1754 with an upperopening 1756 and a circumferential rim 1758 that protrudes into opening1756.

A piston 1760 and coil spring 1780 are mounted in cavity 1754.Specifically, piston 1760 is cylindrical in shape with an inner end 1762and an outer end 1764. An annular flange 1776 surrounds a lower portionof the piston 1760 and is spaced from inner end 1762. A hole 1778extends through an upper portion of the post 1760. A handle 1779 ismounted through hole 1778 and affixed to piston 1760. The coil spring1780 is mounted around the piston 1760. The coil spring 1760 has anupper end that abuts rim 1758 and a lower end that abuts flange 1776.

The coil spring 1780 biases the piston inner end 1762 through one ofconnecting hub holes 1634 and into one of release ring bores 1742 whenone of the hub holes 1634 is in coaxial alignment with one of therelease ring bores. The piston inner end 1762 is normally seated againstterminal wall 1744 (FIG. 56). In this position, piston 1760 prevents therotation of ring gear 1730 relative to connecting hub 1610 such that therotation of input drive shaft 1240 results in the like rotation ofoutput drive shaft 1800.

A user pulls upwardly on handle 1779 resulting in the compression ofcoil spring 1760 and the piston inner end 1762 being removed from therelease ring bore 1742. In this position, ring gear 1730 is free torotate relative to connecting hub 1610 such that the rotation of inputdrive shaft 1240 only results in the rotation of ring gear 1730. Outputdrive shaft 1800 is therefore disconnected from input drive shaft 1240.The first release mechanism 1750 allows a medical practitioner toconnect and disconnect output drive shaft 1800 from input drive shaft1240 so as to move coupler 1900 as will be described later.

Output drive shaft 1800 is described with reference to FIGS. 55, 57A and57B. The output drive shaft 1800 is formed from a single piece of metal.Output drive shaft 1800 is generally cylindrical in shape. The outputdrive shaft 1800 has a center shaft 1801, a proximal end 1802 and adistal end 1804. A disk shaped head 1810 is formed at proximal end 1802.A bore 1812 extends from distal end 1804 in a proximal direction intothe output drive shaft and terminates at step 1814. An inner annularsurface 1816 defines bore 1812. Another bore 1818 extends through head1810 in a distal end direction and is coaxial and contiguous with bore1812. Bore 1812 has a larger diameter than bore 1818.

The output drive shaft 1800 has an outer annular surface 1820. Threadsor grooves 1822 are defined in the outer annular surface 1820 and helixaround the length of shaft 1800 starting at distal end 1802 andterminating at a step 1823 of a flange 1824. The flange 1824 is locatedbetween head 1810 and center shaft 1801. The diameter of flange 1824 issmaller than the diameter of head 1810. The diameter of the center shaft1801 is smaller than the diameter of flange 1824. A circular groove 1826is defined around the circumference of flange 1824 and a step 1827 isalso defined around the circumference of flange 1824. Three equallyspaced apertures 1828 are defined thru head 1810 and extend between thedistal and proximal sides of head 1810. Apertures 1828 receive pins 1726(FIG. 55) that transfer torque from the planetary gear assembly 1700 tooutput drive shaft 1800.

A bearing 1830 (FIG. 55) has a distal face that is seated against thelip 1642 (FIG. 53B) of connecting hub 1610. The output shaft head 1810is positioned in bore 1640 (FIG. 53B) with the distal step 1827 seatedagainst the proximal face of bearing 1830. The center shaft 1801 extendsinto housing bore 1686. The flange 1824 is surrounded and supported forrotary motion by the bore of bearing 1830. A bevel spring washer 1834 ismounted in housing bore 1686 over center shaft 1801 and is seatedagainst step 1823.

FIGS. 55 and 58 illustrate features of a ball nut 1850 that is mountedin bore 1640 and around output drive shaft 1800. The ball nut 1850 is amechanical linear actuator that translates rotational motion to linearmotion with little friction and is able to apply or withstand highthrust loads. The ball nut 1850 has a truncated cylindrical shape with arounded side 1864 and a flat side 1866. Ball nut 1850 has a proximalface 1852 and a distal face 1854. A bore 1856 extends entirely throughthe ball nut between the proximal and distal faces. Spiral horseshoeshaped raceways 1862 are defined within ball nut 1850. Ball bearings1860 are disposed in raceways 1862.

The ball nut 1850 is disposed over output drive shaft 1800. Ballbearings 1860 are loaded into raceways 1862 thru an access port 1867.The bearings 1860 circulate thru raceways 1862 and the grooves 1822 ofoutput drive shaft 1800 as the output drive shaft is rotated. Thethreaded output drive shaft provides a helical raceway for the ballbearings which act as a precision screw. The rotation of output driveshaft 1800 causes a linear translation of ball nut 1850 in either theproximal or distal direction relative to housing 1680 depending upon therotational direction of output drive shaft 1800.

Ball nut 1850 includes a proximal section 1868 that is defined by aproximal facing step 1870. Proximal section 1868 has a smaller diameterthan the remainder of the ball nut. External threads 1872 are defined onproximal section 1868.

FIGS. 55 and 59A-59C show details of a coupler 1900 that is mounted inbore 1640 and to ball nut 1850. Coupler 1900 couples ball nut 1850 totissue protector sleeve 2000. Coupler 1900 is formed from a single pieceof metal and is generally cylindrical in shape. Coupler 1900 has aproximal end 1912 and a distal end 1914. The coupler 1900 has threeadjacent cylindrical sections, a base section 1920, a center section1940 and an end section 1960. The center section 1940 has a diameterthat is less than the diameter of base section 1920. End section 1960has a diameter that is less than the diameter of center section 1940.

The base section 1920 has an outer annular surface 1922 and a bore 1924that is defined by an inner annular surface 1925. Bore 1924 extends fromproximal end 1912 in a distal direction partially into base section 1920terminating at the internal wall 1926. Wall 1926 is perpendicular toinner annular surface 1925. Four elongated slots 1928 are defined in theouter annular surface 1922 and extend the entire length of base section1920. The slots 1928 are spaced equidistant apart around thecircumference of base section 1920. An arcuate rectangular shapedopening 1930 is located on one side of base section 1920 and faces intobore 1924.

A circumferential lip 1932 extends outwardly from the junction of centersection 1940 and end section 1960. Another bore 1942 is defined by aninner annular surface 1944. Bore 1942 extends within the base, centerand top sections in a distal direction from wall 1926 and terminates atthe internal wall 1946. Wall 1946 is perpendicular to inner annularsurface 1944. Bore 1942 is contiguous with bore 1924.

The end section 1960 has a bore 1962 that is defined by an inner annularsurface 1964. Bore 1962 extends from distal end opening 1966 in aproximal direction and terminates at wall 1946. Bore 1962 is coaxial andcontiguous with bore 1942. An angled nose 1968 is formed in end section1960. Nose 1968 angles inwardly from the outer surface of end section1960 and terminates at opening 1966. A rectangular shaped recess 1970 isformed in nose 1968 and has a bottom wall 1972. A threaded aperture 1974extends between the bottom wall 1972 and inner annular surface 1964opening into bore 1962. A rim 1976 extends into aperture 1974 from innerannular surface 1964.

Ball nut 1850 and output shaft 1800 are disposed in coupler bore 1924.The ball nut distal wall 1854 seated against the coupler internal wall1926. The ball nut flat section 1866 faces toward opening 1924. Theaccess port 1867 is accessed through opening 1924. Ball nut 1850 isaffixed to coupler 1900 by suitable methods such as by welding or byusing fasteners. The output shaft 1800 extends into coupler bore 1942with the output shaft distal end 1804 spaced slightly away from internalwall 1946.

A bevel spring washer 1980 (FIG. 55) is mounted over a breech 1982. Thebreech 1982 has internal threads (not shown) that mate with the externalthreads 1872 of ball nut 1850. Breech 1982 surrounds the ball nutproximal section 1868 and extends over the proximal face 1852 andretains the bevel spring washer 1980 to ball nut 1980. Bevel springwasher 1980 is seated between the distal face 1852 and breech 1982.

Turning to FIG. 43, the housing 1680 is mounted over coupler 1900 suchthat the coupler 1900 resides within housing bore 1686. Threaded holes1988 extend thru housing 1680 and are aligned over slots 1928. Screws1990 are fastened in holes 1988 such that the ends of the screws 1990extend into and are located within slots 1928, but are not touching thebottom of slots 1928. During use, coupler 1900 moves linearly withinbore 1686. Screws 1990 disposed in slots 1928 allow linear motion ofcoupler 1900, but prevent rotation of coupler 1900 relative to housing1680.

With reference to FIG. 60, features of tissue protector sleeve 2000 arenow described. The tissue protector sleeve 2000 has an elongated rodshape. Tissue protector sleeve 2000 is formed with a hollow interiorpassage 2010 that is defined by an interior circumferential wall orsurface 2012. The passage 2010 extends through the entire length oftissue protector sleeve 2000. The tissue protector sleeve 2000 has acenter section 2020, a proximal end 2022, a distal end 2024 and an outersurface 2026. An opening 2042 is located at proximal end 2022 and anopening 2024 is located at distal end 2024. A series of parallel grooves2030 are defined on a portion of outer surface 2026 between the centersection 2020 and the proximal end 2022. The grooves 2030 are orientedperpendicular to the longitudinal axis of sleeve 2000.

The tissue protector sleeve 2000 is positioned for sliding movementwithin coupler bores 1942 and 1961 (FIG. 59C) and within output driveshaft bore 1812 (FIG. 57B). In particular, the proximal portion oftissue protector sleeve 2000 is seated in output drive shaft bore 1812and the center section 2020 is positioned within coupler bores 1942 and1961. The outer surface 2026 of tissue protector sleeve 2000 issupported by inner annular surface 1964 (FIG. 59C) for sliding motionwithin bore 1962. The proximal end 2022 of the tissue protector sleeveis received into coupler distal opening 1966 (FIG. 43).

The drill bit 1500 (FIG. 43) is received in sleeve opening 2044 andextends thru bore 2010. The proximal drive head 1520 (FIG. 51) isreceived within input drive shaft D-shaped bore 1252 and bore 1254 (FIG.51). The outer circumferential surface of the drill bit 1500 issurrounded by the inner circumferential surface 2012 of the tissueprotector sleeve 2000. The tissue protector sleeve 2000 can slide in alongitudinal direction relative to drill bit 1500.

A second release mechanism 2100 is illustrated with reference to FIG.61. The second release mechanism 2100 is mounted to the nose 1968 of endcoupler section 1960. Second release mechanism 2100 includes a barrel2110 that is screwed into threads 1976 of aperture 1974. Threads (notshown) are defined on the exterior surface of barrel 2110. Barrel 2110has a hollow cylindrical shaped interior cavity 2112 with and a lowercircumferential rim 2114 that protrudes into cavity 2114 at the end ofbarrel 2110.

A detent arm 2120 and coil spring 2140 are mounted in cavity 2112.Specifically, the detent arm 2120 has a tapered cylindrical shape withan inner end 2122 and an outer end 2124. The inner end 2122 has a largerdiameter that the outer end 2124. An annular flange 2126 surrounds innerend 2122. A detent finger 2126 extends away from the inner end 2122.Detent finger 2126 is dimensioned so as to fit into the sleeve grooves2030. A threaded hole 2128 extends through detent arm 2120 at outer end2124. The coil spring 2140 is mounted around the detent arm 2120. Thecoil spring 2140 has an upper end that abuts flange 2126 and a lower endthat abuts rim 2114.

The coil spring 2140 biases the detent arm towards tissue protectorsleeve 1900 and when the detent finger 2126 is aligned with one of thesleeve grooves 2030, urges the detent finger 2126 to be seated in thecorresponding aligned groove 2030.

A knob 2150 is connected to detent arm 2120. Knob 2150 is positioned inrecess 1970 and rests on the bottom wall 1972. Knob 2150 is generallyrectangular in shape and can be formed from injection molded plastic.Knob 2150 has an internal chamber 2152 that faces bottom wall and aninternal bore 2154 that intersects with and is perpendicular to chamber2152. A counter-bore 2156 extends from the distal side of the knob andterminates at the intersection with internal bore 2154. Counter-bore2156 is coaxial with internal bore 2154.

Knob 2150 is held to detent arm 2120 by a screw 2160. Screw 2160 extendsthrough counter-bore 2156, internal bore 2154 and is received intothreaded hole 2128. The head of screw 2160 is seated in counter-bore2156 such that the distal face of knob 2150 and the head of the screware flush.

The detent finger 2126 is normally seated, due to the bias of coilspring 2140, in a corresponding aligned groove 2030. In this position,the tissue protecting sleeve 2000 is connected or locked to thecombination of coupler 1900 and ball nut 1850 by the second releasemechanism 2100 such that linear movement of the coupler 1900 in aproximal or distal direction results in a like movement of tissueprotecting sleeve 2000 in respective proximal or distal directions.

A medical practitioner grasps the distal portion of knob 2150 and movethe distal portion of the knob towards or away from coupler nose 1968.Movement of the distal portion of the knob towards or away from couplernose 1968 results in a lever arm force being applied to detent arm 2120that moves the detent arm 2120 away from sleeve 2000 and also movesdetent finger 2126 out of engagement with grooves 2130. Coil spring 2140is also compressed by the lever arm force. In this position, the tissueprotector sleeve 2000 is free to slide relative to both drill bit 1500and coupler 1900.

When the distal portion of knob 2150 is released, spring 2140 urges thedetent finger 2126 to be seated or engaged with a corresponding alignedsleeve groove 2030. This locks tissue protecting sleeve 2000 to thecombination of coupler 1900 and ball nut 1850.

Release mechanism 2100 allows the practitioner to connect and disconnectthe tissue protector sleeve from coupler 1900. This allows slidingmovement of tissue protector sleeve 2000 relative to drill bit 1500.

The remaining components of rotary surgical drill 1100 includingcontroller 450 and the electrical connections shown in the electricalschematic (FIG. 13) are the same as previously described for rotarysurgical drill 100 except that the solenoid 252 and digital caliper 400have been omitted. Controller 450 controls the operation of brakingmechanism 1150.

C. Operation

FIG. 62A illustrates the rotary surgical drill 1100 being used at asurgical site 2200. The medical practitioner grasps handle 104 anddirects the drill bit tip 1514 to the surgical site. Drill bit 1500 isused to drill one or more bores into a bone.

With reference to FIGS. 44A, 44B and 55, the rotary surgical drill 1100is initially prepared for drilling a bone bore by the medicalpractitioner attaching chuck assembly 1200 to handpiece 102 (FIG. 42)and attaching a drill bit 1500 to chuck assembly 1200 using drill bitretainer assembly 1275.

Next, the first release mechanism 1750 is set to disconnect the outputdrive shaft 1800 from input drive shaft 1240. The medical practitionerpulls upwardly on handle 1779 resulting in the compression of coilspring 1760 and the piston inner end 1762 being removed from one ofrelease ring bores 1742. In this position, ring gear 1730 is free torotate relative to connecting hub 1610 such that the rotation of theinput drive shaft 1240 only results in the rotation of ring gear 1730and the output drive shaft 1800 is disconnected from the input driveshaft 1240. Also, in this position the combination of the coupler 1900and the ball nut 1850 are free to slide in a proximal or distaldirection relative to housing 1680.

The medical practitioner grasps the coupler end section 1960 andmanually moves the coupler 1900 to a distal most position or fullyextended position as shown in FIGS. 44A and 44B. The movement of coupler1900 in the distal direction is limited by the abutment of bevel springwasher 1980 against screws 1990. The movement of coupler 1900 is guidedby the ends of screws 1990 tracking within coupler slots 1928 (FIG.59A).

With the coupler 1900 fully extended, the medical practitioner releaseshandle 1779. This causes spring 1780 to displace piston 1760 so thepiston inner end 1762 is urged through one of connecting hub holes 1634and into one of release ring bores 1742. The piston end 162 seatsagainst terminal wall 1744 (FIG. 56). In this position, piston 1760prevents the rotation of ring gear 1730 relative to connecting hub 1610such that the rotation of input drive shaft 1240 results in the likerotation of output drive shaft 1800. The input drive shaft 1240 is nowre-connected to output drive shaft 1800.

The medical practitioner next prepares rotary surgical drill 1100 fordrilling a bone bore by positioning the tissue protector sleeve 2000relative to drill bit 1500 such that a desired length of the drill bittip 1514 extends beyond the sleeve distal end 2024. The tissue protectorsleeve 2000 is positioned using second release mechanism 2100 (FIG. 61).With additional reference to FIG. 61, the medical practitioner graspsthe distal portion of knob 2150 and moves the distal portion of the knobtowards or away from coupler nose 1968. The movement of the distalportion of the knob towards or away from coupler nose 1968 results in alever arm force being applied to detent arm 2120. This force moves thedetent arm 2120 away from sleeve 2000 and also moves detent finger 2126out of engagement with grooves 2130. The tissue protector sleeve 2000 ismanually grasped and moved in either a distal or proximal directionrelative to the drill bit 1500 such that a desired length of the drillbit tip 1514 extends beyond the sleeve distal end 2024. In oneembodiment, the tissue protector sleeve 2000 is positioned such that thedistal end 2024 is slightly drawn back from the drill bit distal tip1514 causing only the distal tip 1514 to be exposed as seen in FIG. 62A.

The medical practitioner releases the distal portion of knob 2150.Spring 2140 then urges detent finger 2126 into engagement with acorresponding aligned sleeve groove 2030 This locking the tissueprotecting sleeve 2000 to the combination of coupler 1900 and ball nut1850. The rotary surgical drill 1100 is now ready to drill a bone bore

With additional reference to FIGS. 13 and 62A, the surgical drill 1100is used at a surgical site 2200 to form a bore in a bone. The drill bittip 1514 is positioned against the proximal side 492 of the bone 490where a bone bore is to be formed. Also initially, the drill bit 1500 isnot subjected to any axial loading.

The drill bit 1500 is forced downwardly by the medical practitioner inan axial direction. After the drill bit 1500 is so positioned, therotary drill 1100 is actuated in a forward or clockwise rotation.

The combination of the rotating drill bit and the axial load placed onthe drill bit results in the cutting edges of the drill bit tip 1514cutting the bone 490 so as to form a bore 498 (FIG. 62B). Sensor 464operates as described with the previous versions of the invention.

Referring to FIG. 61B, as the drill bit tip 1514 enters the bone, thedistal end 2024 of the tissue protector sleeve 2000 abuts the proximalside 492 of bone 490 limiting the forward movement of drill bit 1500.

At the same time that the drill bit 1500 is rotated by motor 122, themotor 122 drives the retracting sleeve mechanism 1600. Specifically,motor 122 rotates input drive shaft 1240 driving the first and secondstages of planetary gear assembly 1700. This results in the rotation ofoutput drive shaft 1800. The rotation of the output drive shaft 1800causes a linear translation of the ball nut 1850 and the attachedcoupler 1900 in the proximal direction relative to housing 1680. Thecoupler 1900 and ball nut 1850 retract into housing bore 1686. Becausethe tissue protector sleeve 2000 is coupled to coupler 1900 by thesecond release mechanism 2100, translation of the coupler 1900 in theproximal direction causes the tissue protector sleeve 2000 to retractaway from the drill bit tip 1514.

In practice the ball screw rotates at a speed of between 50 to 200 RPM.Often this rotation is between 75 and 125 RPM. The pitch of ball screwis selected so that the screw causes the sleeve 2000 to retract at aspeed of between 2.5 mm/sec. to 8.0 mm/sec. More often, the componentsforming the retraction mechanism are set so that screw causes the sleeveto retract at a rate of between 3.5 mm/sec. and 6.5 mm/sec.

Therefore, as the bone bore 498 is formed, the length of the drill bit1500 exposed or extending beyond the distal end 2024 of the tissueprotector sleeve increases. During drilling of the bone bore, the tissueprotector distal end 2024 remains static against the bone 490 while thehandpiece, chuck assembly 1200 and housing 1680 move in a distaldirection relative to coupler 1900 during drilling.

Referring to FIGS. 45A and 45B, the retraction of the tissue protectingsleeve 2000 and coupler 1900 into the housing bore 1686 is limited bythe abutment of the proximal face of breech 1982 against the bevelspring washer 1834. As shown in FIGS. 45A and 45B, the coupler 1900 isin a proximal most position or fully retracted into housing 1680 suchthat only a portion of coupler end 1960 extends beyond the distal end1684 of the housing. In this position, the maximum length of the distalend of the drill bit 1500 extending beyond the distal end 2024 of thetissue protecting sleeve is revealed.

With additional reference to FIGS. 13 and 61C, continued rotation of thedrill bit and axial loading causes the drill bit tip 1514 to penetratethrough the bone and bone marrow 496 and to approach the distal side 494of bone 490. Eventually, the drill bit tip 1514 cuts through the distalside 494 of bone 490. As described above with respect to the otherversions of the invention, sensor 464 detects the change in current drawand asserts a signal to controller 450.

In response to the change in current drawing being greater than thethreshold change in current level, braking mechanism 1150 throughprocessor 452 turns off motor 122 through motor driver circuit 462. Whenthe motor 122 is turned off, the tissue protector sleeve 200 will nolonger be retracted. This prevents further advancement of the drill bit1500. Further the turning off of motor 122 also stops the rotation ofthe drill bit 1500. Collectively, the stopping of these movementsprevents further advancement of the drill bit beyond the distal side 494of the bone.

After the braking mechanism 1150 has stopped advancement of the drillbit 1500, the length of the drill in the bone bore 498 is equal to thedistance between the distal end 2024 of the tissue protector sleeve andthe drill bit tip 1514. This length is the approximate length that isrequired for a bone screw that is to be inserted into the bone bore.

The medical practitioner may pull the drill bit 1500 out from the bonebore 498. However, if the bone bore is deep, the frictional forceimposed by the bone may significantly impede the withdrawal of the bit1500. To break this frictional force, drill 1100 can be actuated drivethe bit in either the forward or reverse direction.

Should the practitioner choose to actuate drill 1100 so the bit 1500 isrotated in the reverse direction, brake mechanism 1150 simultaneouslyadvances sleeve 2000 in the distal direction. This repositions thesleeve 2000 so that the distal end of the sleeve is located relativelyclose to the tip 1514 of the drill bit 1500. Thus an advantage ofdriving the drill 1100 in the reverse direction to withdraw the bit, isthat at the end of the process sleeve 2000 is essentially repositionedto again function as stop that prevents overdrilling of the next bore.

With the drill bit 1500 removed from the bone bore, the medicalpractitioner can place bone screws adjacent the drill bit portion thatextends beyond the distal end 2024 of the tissue protector sleeve andvisually select the bone screw that matches the depth of the bone bore.Alternatively, the medical practitioner can use a measurement scale tomeasure the drill bit portion that extends beyond the distal end 2024 ofthe tissue protector sleeve.

In some procedures, it may be necessary to use drill 1100 to drillplural bores in the patient. Between the drilling of two bore, it isoften desirable to reset sleeve 2000 to the extended position. One meansby which sleeve 2000 may be so extended is, once the bit 1500 is removedfrom the patent, reengaging the release mechanism and then, while thebit is out of the patient, driving the drill in reverse. This results inrelease mechanism 1600 advancing the sleeve 2000 distally forward overthe bit 1500. This method assumes that the release mechanism 1600 isengaged with the planetary gear assembly.

Alternatively, when the handle 1779 is in the disengaged state, sleeve2000 can simply be manually extended over the drill bit 1500. Once thesleeve 2000 is so positioned, handle 1779 is reset to the engaged state.Drill 1100 is again ready for use.

Before the medical practitioner can use rotary surgical drill 1100 toform another bore, the braking mechanism 1150 is reset to allow rotationof motor 122 in a forward direction. In one embodiment, processor 452allows forward rotation of motor 122 after sensing depression of reversetrigger switch 117. In another embodiment, processor 452 allows forwardrotation of motor 122 after detecting a certain sequence of depressionof the trigger switches 116, 117. For example, processor 452 can resetbraking mechanism 1150 after detecting the simultaneous depression ofboth trigger switches 116 and 117. In an additional embodiment, aseparate switch (not shown) can be provided to reset braking mechanism1150.

The braking mechanism 1150 of the present invention using retractingsleeve mechanism 1600 allows a drill bit 1500 that is forming a bonebore to stop further penetration beyond the bone after the initialpenetration through the bone, thereby preventing damage to any tissueadjacent the distal side of the bone. After the drill bit 1500 has cutthrough the bone, the drill bit 1500 stops rotating in a forwarddirection thereby avoiding cutting any tissue adjacent to the distalside of the bone bore.

The above description is directed to specific versions of the invention.Other versions of the invention may have features different from whathas been described. For example components from the various versions ofthe inventions may be combined.

Further sensors other than sensors that simply monitor changes incurrent draw may be used to provide the signal indicating that the drillbit penetrated the side of the bone not visible to the practitioner.These sensors include force sensors that monitor the force applied whenpushing the drill bit forward. A signal indicating the sudden drop offin applied force would be interpreted as an indication that the drillbit has completely penetrated the bone. Still another type of sensorthat may be used to provide a signal indicative of drill bit penetrationis a sensor that monitors the torque applied by the drill bit. Sensorsother than sensors that operate by measuring current draw can provide ameasure of drill bit torque. A signal from this type of sensorindicating that the quantity of torque output by the drill bit hassignificantly dropped in a short amount of time is interpreted as anindication that the drill bet has fully penetrated the bone. Stillanother type of sensor that may be employed to provide an indication ofdrill bit penetration is an accelerometer. This type of sensing may beuseful because, as the drill bit penetrates the bone, there is a rapidacceleration of the bit and handpiece 102. Accordingly, the signal fromthe accelerometer could be used to provide this indication that thedrill bit has penetrated bone.

The above sensors are often used in versions of this invention whereinthe handpiece motor is a motor other than an electrically driven motor.These motors include pneumatic and hydraulically driven motors.

In some versions of the invention, the stop at the distal end of thetelescoping rod 360 may not be a ring 378 that extends around the drillbit. Instead the stop may be a small tab that projects from the rod 360.Alternatively the stop may simply be the distal end of the rod 360.

A device other than a solenoid may move the brake between the engagedand disengaged states. These devices include stepper motors. In theseversions of the invention, the actuator in addition to moving the brakefrom the disengaged to the engaged state can be run in reveres to movethe brake from engaged to the disengaged state. This would eliminate theneed to provide a spring or other biasing component to hold the brake inthe disengaged state. In still other versions of the invention thespring may normally bias the brake into the engaged state. In theseversions of the invention, the solenoid or other actuator, in oppositionto the spring force normally holds the brake in the disengaged state.Upon receiving the command signal that the brake is to be set, theactuator releases the force holding the brake. The spring or otherbiasing component provides the force that drives the brake intoengagement with the rack.

In versions of the invention wherein the telescoping member thatretracts with the actuation of the motor, this member may not always bea sleeve. In alternative versions of this invention this telescopingmember may be a single rod to which a stop is attached. Alternatively,this telescoping member can be plural rods that surround the drill bit.A single stop may be attached to the distal ends of these rods.

Similarly, it should be understood that the direction of movement of thebrake from the disengaged state to the engaged state may vary from whathas been described. Thus there is no requirement that when the brake isso displaced, the brake move either towards the handle 104 or away fromthe handle 104. In some versions of the invention, the brake may movealong a path of travel that is perpendicular to the top to bottomlongitudinal axis through the handle.

Accordingly, it is an object of the appended claims to cover allvariations and modifications that come within the true spirit and scopeof this invention.

What is claimed is:
 1. A surgical drill assembly comprising: a handpiecewith a motor, a chuck attached to the motor for releasably holding adrill bit to the motor so the drill bit can be rotated by the motor; atelescoping member having opposed proximal and distal ends, a proximalsection of the telescoping member moveably mounted to the handpiece toallow the telescoping member to move proximally and distally along thehandpiece and a stop attached to the distal end of the telescopingmember so as to be located at a distal end of the drill assembly; abrake assembly is attached to said handpiece, said brake assemblyincluding a member having: a brake that is moveably attached to saidhandpiece to move between engaged and disengaged positions with thetelescoping member, wherein when the brake is in the engaged positionwith the telescoping member, said brake stops movement of thetelescoping member; and an actuator, that in response to a commandsignal, selectively moves said brake from the disengaged position to theengaged position; wherein the telescoping member comprises a pluralityof teeth, and the brake comprises a plunger moveable between the engagedand disengaged positions, such that the plunger is configured to engagethe teeth of the telescoping member when the plunger is in the engagedposition and the plunger is configured to disengage the teeth of thetelescoping member when the plunger is in the disengaged position. 2.The surgical drill of claim 1, wherein: the handpiece has an end: andsaid brake and said actuator are mounted to the handpiece so as to belocated adjacent to the end of said handpiece.
 3. The surgical drillassembly of claim 1, wherein: said plurality of teeth of saidtelescoping member extends proximally to distally along the telescopingmember; and said brake is formed with a tooth dimensioned to, when thebrake is in the engaged position seat between said plurality of teeth ofsaid telescoping member.
 4. The surgical drill assembly of claim 1further including the actuator that normally holds the brake in thedisengaged position.
 5. The surgical drill assembly of claim 1, whereinsaid actuator is a solenoid.
 6. The surgical drill assembly of claim 1,wherein: a sensor is mounted to said handpiece to monitor when saiddrill bit penetrates through bone and asserts a sensor signal indicativeof when the drill penetrates through bone; a control circuit is mountedto said handpiece to receive from said sensor the sensor signalindicative of when said drill bit penetrates through bone and, inresponse to receipt of the sensor signal, asserts the command signal tosaid actuator that causes said actuator to move said brake from thedisengaged position to the engaged position.
 7. The surgical drillassembly of claim 6, wherein said motor is an electrically poweredmotor; and said sensor is configured to monitor when the drill bitpenetrates bone by monitoring current draw of said motor.
 8. Thesurgical drill assembly of claim 1, further including a depth gaugemounted to the handpiece to monitor the movement of the telescopingmember.
 9. A surgical drill assembly comprising: a handpiece with amotor, a chuck attached to said motor for releasably holding a drill bitto said motor so the drill bit can be rotated by the motor; atelescoping member having opposed proximal and distal ends, a proximalsection of the telescoping member moveably mounted to the handpiece toallow the telescoping member to move proximally and distally along thehandpiece and a stop attached to the distal end of the telescopingmember so as to be located at a distal end of the drill assembly, whereat least a portion of said telescoping member is located proximal to thedrill bit and is at least partially contained in the handpiece; and abrake that is moveably attached to said handpiece to move betweenengaged and disengaged positions with the telescoping member, whereinwhen the brake is in the engaged position with the telescoping member,said brake stops movement of the telescoping member; and an actuator,that in response to a command signal, selectively moves said brake fromthe disengaged position to the engaged position; said motor has a rotorwith an axially extending throughbore; a portion of said telescopingmember is slidably disposed in the throughbore of the motor rotor andextends out of a proximal end of the motor rotor; and said brake ismounted to the handpiece so as to be located proximal to the motor so asto engage a portion of the telescoping member that extends proximallyfrom the motor.
 10. A surgical drill comprising: a handpiece with amotor, a chuck attached to the motor for releasably holding a drill bitto the motor so the drill bit can be rotated by the motor; a telescopingmember having opposed proximal and distal ends, a proximal section ofthe telescoping member moveably mounted to the handpiece to allow thetelescoping member to move proximally and distally along the handpiece,the distal end shaped to abut tissue adjacent tissue into which thedrill bit bores; and a retraction assembly attached to the telescopingmember and capable of, simultaneously with actuation of the motor torotate the drill bit retracting the telescoping member proximally so thedistal end of the telescoping member is retracted proximally away from adistal end tip of the drill bit, wherein said retraction assembly isconnected to said motor so that said motor, simultaneously with therotation of the drill bit, causes the retraction assembly to retract thetelescoping member proximally; wherein the telescoping member is asleeve that is disposed over the drill bit.
 11. The surgical drillassembly of claim 1, wherein the actuator comprises a solenoidconfigured to be energized and move the plunger to the engaged positionwhere the plunger engages with the plurality of teeth of the telescopingmember.